A modified single-crystalline ternary cathode material, a preparation method thereof, and a lithium-ion battery containing the modified single-crystalline ternary cathode material

Abstract

The present invention discloses a modified single-crystalline ternary cathode material, a preparation method, and a battery containing the material. The cathode material includes a matrix material and a coating material coated on its surface; the matrix material is a single-crystalline ternary cathode material LiNi a Co b Mn 1‑a‑b O2, where 0.7 ≤ a < 1, 0 < b < 0.2, and 1 - a - b > 0; the coating material includes a liquid crystal polyurethane / Ce x Y 0.4‑x Fe y Co 4‑y M 12 composite layer, where 0.1 ≤ x < 0.4 and 0 < y < 4, and M is at least one of Sb, P, and As. In the preparation method of the present invention, a composite coating layer is obtained by dynamically coating liquid crystal polyurethane on the surface of the single-crystalline ternary material during the pulverization process. The composite coating layer effectively inhibits the generation of inactive Ni ions and the escape of oxygen during the process of lithium extraction, reduces the increase in the DCR value of the cathode material when assembling the battery at high temperature and high cut-off voltage, and improves the high-temperature storage performance of the battery.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and particularly relates to a modified single-crystalline ternary cathode material, a preparation method thereof, and a lithium-ion battery containing the modified single-crystalline ternary cathode material. Background Art

[0002] With the accelerating development of new energy vehicles, nickel-cobalt-manganese (NCM) ternary cathode materials, especially high-nickel (nickel content ≥ 70%) and low-cobalt single-crystalline ternary cathode materials, as a rising star, have attracted great interest in the academic and industrial circles due to their comprehensive performance and cost indicators being superior to those of polycrystalline ternary cathodes and lithium iron phosphate materials.

[0003] However, there are inactive Ni ions (including divalent and trivalent) in the high-nickel and low-cobalt single-crystalline ternary cathode material after long-term cycling at high temperature. The inactive Ni 2+ mainly comes from the NiO-like phase concentrated at grain boundaries and grain surfaces, and a part of the inactive Ni 3+ may come from the lithium-deficient phase NiO2. Due to the existence of inactive Ni ions, oxygen may escape during the process of lithium extraction, resulting in a sharp increase in DCR of the battery prepared from the material during long-term cycling at high temperature, leading to obvious cycle attenuation. In order to improve the performance of the ternary cathode material, common methods include coating modification. For example, the Chinese patent application document with the publication number CN112864369A discloses a modified high-nickel ternary cathode material and a preparation method thereof, which coats the high-nickel ternary material with a carboxylic acid-type polyurethane prepolymer as the coating layer, consumes the residual alkali on the surface of the high-nickel ternary material while preparing the carboxylic acid-type polyurethane prepolymer for the coating layer, and the prepared carboxylic acid-type polyurethane prepolymer can improve the electrochemical performance of the modified high-nickel ternary cathode material and reduce costs at the same time, having application prospects. However, it does not mention whether the carboxylic acid-type polyurethane for coating modification can solve the problem of high DCR growth of the single-crystalline ternary cathode material at high temperature and high cut-off voltage, and high DCR will directly affect the battery performance, thereby further affecting the cruising range of the application vehicle. Therefore, it is particularly important to provide a single-crystalline ternary cathode material whose prepared battery has a low DCR value growth under high cut-off voltage and long-term cycling at high temperature. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a single-crystalline ternary cathode material with good cycle stability under high temperature and high cut-off voltage and a preparation method thereof.

[0005] The present invention solves the above technical problems by the following technical means:

[0006] A modified single-crystalline ternary cathode material, comprising a matrix material and a coating material coated on the surface of the matrix material; the matrix material is a single-crystalline ternary cathode material LiNia Co b Mn 1-a-b O2, where 0.7 ≤ a < 1, 0 < b < 0.2, and 1 - a - b > 0; the coating material includes liquid crystal polyurethane / Ce x Y 0.4-x Fe y Co 4-y M 12 composite layer, where 0.1 ≤ x < 0.4, 0 < y < 4, and M is selected from at least one of the elements Sb, P, and As.

[0007] Preferably, the thickness of the coating material is 25 - 50 nm.

[0008] The present invention also provides a method for preparing the modified single-crystalline ternary cathode material, comprising the following steps:

[0009] S1. Using cerium powder, yttrium powder, iron powder, cobalt powder, and M powder as starting materials, weighing them according to the chemical stoichiometric ratio of Ce:Y:Fe:Co:M elements as x:0.4 - x:y:4 - y:12, and obtaining a composite material after ball milling;

[0010] S2. Stirring and mixing the composite material obtained in S1 with the single-crystalline ternary cathode precursor Ni a Co b Mn 1-a-b (OH)2, and then placing the mixed material in a spark plasma sintering furnace for heat preservation sintering to obtain a modified precursor, i.e., Ce x Y 0.4- x Fe y Co 4-y M 12 coated Ni a Co b Mn 1-a-b (OH)2;

[0011] S3. Stirring and mixing the modified precursor obtained in S2 with a lithium source, and sintering in an oxygen atmosphere to obtain a sintered material;

[0012] S4. Crushing the sintered material obtained in S3 and then grinding it to obtain a crushed material with a spherical and / or quasi-spherical microscopic morphology;

[0013] S5. Stirring and mixing a hydroxy liquid crystal monomer, trimethylolpropane polyethylene glycol monomethyl ether, and the crushed material obtained in S4 to obtain a mixed material;

[0014] S6. Keeping the temperature of the honeycomb mill crushing cavity, adjusting the main machine speed, adding the mixed material obtained in S5, and introducing a mixed gas, and obtaining the modified single-crystalline ternary cathode material after crushing, where the mixed gas is a mixture of heated isocyanate and nitrogen;

[0015] Among them, in S1 and S2, 0.1 ≤ x < 0.4, 0 < y < 4, and M is selected from at least one of the elements Sb, P, and As; in S2, 0.7 ≤ a < 1, 0 < b < 0.2, and 1 - a - b > 0.

[0016] Preferably, in S1, the rotation speed of the ball milling is 500 - 900 r / min, the time is 2 - 4 h, and the median particle size of the composite material is 100 - 500 nm; in S2, during the stirring and mixing process, the rotation speed is 200 - 800 r / min, and the mixing time is 1 - 2 h; in S3, during the stirring and mixing process, the rotation speed is 200 - 500 r / min, and the mixing time is 30 - 60 min; in S5, during the stirring and mixing process, the rotation speed is 100 - 200 r / min, and the mixing time is 10 - 40 min.

[0017] Preferably, in S2, the mass ratio of the composite material to the single-crystalline ternary cathode precursor Ni a Co b Mn 1-a-b (OH)2 is 1:500 - 1000; the thickness of the modified precursor Ce x Y 0.4-x Fe y Co 4-y M 12 coating Ni a Co b Mn 1-a-b (OH)2 is 5 - 10 nm for Ce x Y 0.4- x Fe y Co 4-y M 12 ; in S3, the mass ratio of the modified precursor to the lithium source is 2.12 - 2.54:1; in S5, the mass ratio of the hydroxy liquid crystal monomer, trimethylolpropane polyethylene glycol monomethyl ether, and crushed material is 1:1.2 - 2.4:50 - 160.

[0018] Preferably, in S2, during the heat preservation and sintering process, the temperature is 500 - 1000 K, the sintering pressure is 5 - 10 MPa, and the time is 10 - 25 min; in S3, the sintering temperature is 800 - 900 °C, and the time is 10 - 20 h.

[0019] Preferably, in S4, the sintered material is crushed and then put into a stone mortar mill. The gap between the upper and lower grinding plates is adjusted to 100 - 300 μm for primary grinding, and the material after primary grinding is collected. Then, the gap between the upper and lower grinding plates is adjusted to 20 - 50 μm, and the material after primary grinding is put in for secondary grinding to obtain a secondary ground material with a spherical or quasi-spherical micro-morphology and an aspect ratio of major axis to minor axis of 1.2 - 1.9:1, that is, the crushed material.

[0020] Preferably, in S6, the temperature inside the crushing cavity of the honeycomb mill is maintained at 60 - 95 °C, and the main machine speed of the honeycomb mill is 1600 - 2400 r / min. The mixed material and the mixed gas are synchronously input into the crushing cavity of the honeycomb mill, where the input speed of the mixed material is 20 - 40 kg / h, and the input flow rate of the mixed gas is 40 - 120 m 3 / h. The mixed gas is a mixture of isocyanate heated to 260 - 300 °C and nitrogen, and the volume ratio of isocyanate to nitrogen in the mixed gas is 1:1500 - 2000.

[0021] Preferably, in S3, the lithium source is at least one of lithium hydroxide, lithium carbonate, lithium hexafluorophosphate, and lithium perchlorate. In S5, the hydroxy liquid crystal monomer is 4 - ((6 - hydroxyhexyl)oxy)phenyl 4 - ((6 - hydroxyhexyl)oxy)benzoate, and the structural formula of 4 - ((6 - hydroxyhexyl)oxy)phenyl 4 - ((6 - hydroxyhexyl)oxy)benzoate is as follows: In S6, the isocyanate is a diisocyanate, and the diisocyanate is at least one of hexamethylene diisocyanate, toluene diisocyanate, and isophorone diisocyanate. In S6, the median particle size of the modified single - crystal ternary cathode material is 2 - 5 μm.

[0022] Preferably, in S1, the purities of the cerium powder, yttrium powder, iron powder, cobalt powder, and M powder are 98.9 - 99.9%.

[0023] Preferably, in S4, the median particle size of the crushed sintered material is 1 - 3 mm.

[0024] Preferably, in S4, the crushing is performed using at least one of a rotary wheel mill, a jaw crusher, and a pair - roll crusher.

[0025] Preferably, in S6, the discharge port of the honeycomb mill is connected to a trap and a fan in sequence through a pipeline. The fan runs synchronously with the honeycomb mill to continuously convey the modified single - crystal ternary cathode material from the honeycomb mill to the trap.

[0026] Preferably, the honeycomb grinder has a vertically installed depolymerization wheel with 5 to 15 stages. Each stage of the depolymerization wheel consists of 100 to 200 blades clamped by two support discs mounted on the main shaft. During the operation of the honeycomb grinder, the blades rotating at high speed can form multiple nested swirls in the crushing chamber, thereby effectively crushing the broken materials.

[0027] The present invention also provides a lithium-ion battery, which includes a positive electrode, a negative electrode, a separator and an electrolyte. The positive electrode contains the modified single-crystalline ternary positive electrode material described above.

[0028] The advantages of the present invention are as follows:

[0029] In the preparation method of the present invention, firstly, rapid and uniform coating of Ce x Y 0.4-x Fe y Co 4-y M 12 is achieved on the surface of the single-crystalline ternary positive electrode precursor through spark plasma sintering. After sintering, materials with a spherical and / or quasi-spherical microscopic morphology are obtained through secondary grinding using, for example, a stone mill. The unique multiple nested swirls of the honeycomb grinder can most effectively crush the spherical or quasi-spherical particles after grinding without damaging the particles. In addition, during the crushing process of the honeycomb grinder, the Ce x Y 0.4-x Fe y Co 4-y M 12 coated on the surface of the spherical or quasi-spherical particles effectively inhibits the crystallinity of the generated liquid crystal polyurethane, and realizes the dynamic coating of the liquid crystal polyurethane during the crushing process, so that the liquid crystal polyurethane / Ce x Y 0.4-x Fe y Co 4-y M 12 composite layer coats the single-crystalline ternary positive electrode material more uniformly and effectively.

[0030] In the modified single-crystalline ternary positive electrode material prepared by the present invention, using the single-crystalline ternary positive electrode material LNCM (LiNi a Co b Mn 1-a-b O2) as the matrix material, the unique structure of the honeycomb grinder is used to dynamically coat the liquid crystal polyurethane / Ce x Y 0.4-x Fe y Co 4-y M 12 composite layer on its surface during the crushing process of the single-crystalline ternary material. The liquid crystal polyurethane / Ce x Y 0.4-x Fe y Co 4-y M 12The composite layer effectively inhibits the generation of inactive Ni ions in the cathode material and the escape of oxygen during the process of lithium extraction, reduces the DCR growth rate of the assembled battery at high temperature and high cut-off voltage, and improves the cycle stability of the battery. Description of the Drawings

[0031] Figure 1 It is the DCR growth rate curve of the battery prepared from the single-crystalline ternary cathode material prepared in Example 1 and Comparative Example 1 of the present invention under the conditions of 3.0 - 4.7V, 50°C, and 200-week cycle.

[0032] Figure 2 It is the microscopic morphology test diagram of the single-crystalline ternary cathode material prepared in Example 1 of the present invention.

[0033] Figure 3 It is the microscopic morphology test diagram of the single-crystalline ternary cathode material prepared in Comparative Example 1 of the present invention. Detailed Description of the Invention

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0035] The test materials and reagents used in the following embodiments can be obtained from commercial sources without special instructions.

[0036] For those not specifying specific techniques or conditions in the embodiments, they can all be carried out according to the techniques or conditions described in the literature in this field or according to the product specifications.

[0037] Example 1

[0038] The modified single-crystalline ternary cathode material in this example is a liquid crystal polyurethane / Ce 0.12 Y 0.28 Fe2Co2Sb 12 Composite layer-coated modified single-crystalline cathode material LiNi 0.7 Co 0.1 Mn 0.2 O2, and the specific preparation method includes the following steps:

[0039] S1. Weigh cerium powder with a purity of 98.9%, yttrium powder with a purity of 99%, iron powder with a purity of 99.9%, cobalt powder with a purity of 99.9%, and antimony powder with a purity of 99.4% according to the elemental stoichiometric ratio of Ce:Y:Fe:Co:Sb being 0.12:0.28:2:2:12 respectively, and ball mill them at a rotation speed of 900 r / min for 4 h to obtain composite material I with a median particle size of 500 nm;

[0040] S2. Weigh composite material I and single-crystalline ternary cathode precursor Ni 0.7 Co 0.1 Mn 0.2 (OH)2 according to a mass ratio of 1:500, and stir and mix them at a rotation speed of 800 r / min for 1 h; Place the mixed material in a spark plasma sintering furnace, and sinter it at 1000 K, a sintering pressure of 8 MPa, and keep the temperature for 25 min to obtain Ce 0.12 Y 0.28 Fe2Co2Sb 12 coated with Ni 0.7 Co 0.1 Mn 0.2 (OH)2, named modified precursor II, where the thickness of the Ce 0.12 Y 0.28 Fe2Co2Sb 12 coating layer is 10 nm;

[0041] S3. Weigh modified precursor II and lithium hydroxide according to a mass ratio of 2.12:1, stir and mix them at a rotation speed of 500 r / min for 60 min, and then place them in a roller hearth kiln. Under an oxygen atmosphere, keep the temperature at 800 °C for 20 h to obtain sintered material III;

[0042] S4. Crush sintered material III with a rotary wheel mill to obtain crushed material with a median particle size of 3 mm, then put it into a stone mortar mill, adjust the gap between the upper and lower grinding discs to 300 μm, and conduct primary grinding for 10 min to collect the material after primary grinding; Then adjust the gap between the upper and lower grinding discs to 20 μm, put the material after primary grinding for secondary grinding for 5 min to obtain spherical secondary ground material with an aspect ratio of 1.2:1, that is, crushed material IV;

[0043] S5. Weigh 4-((6-hydroxyhexyl)oxy)phenyl 4-((6-hydroxyhexyl)oxy)benzoate, trimethylolpropane polyethylene glycol monomethyl ether, and crushed material IV according to a mass ratio of 1:1.2:160, and stir and mix them at a rotation speed of 100 r / min for 40 min to obtain mixture V;

[0044] S6. Preheat the internal temperature of the honeycomb mill crushing cavity to 65 °C, uniformly input mixture V at 20 kg / h and simultaneously at 120 m 3The flow rate of / h is introduced into a mixture of hexamethylene diisocyanate heated to 300 °C and nitrogen with a volume ratio of 1:1500. The main machine speed is controlled at 1600 r / min, and liquid crystal polyurethane / Ce with a median particle size of 2.0 μm is obtained after pulverization. 0.12 Y 0.28 Fe2Co2Sb 12 The obtained modified single-crystalline ternary cathode material is continuously transported to a trap under the action of a blower suction, and finally collected by the trap.

[0045] Example 2

[0046] The modified single-crystalline ternary cathode material in this example is liquid crystal polyurethane / Ce with a thickness of 50 nm. 0.12 Y 0.28 Fe 1.2 Co 2.8 As 12 The single-crystalline cathode material LiNi 0.8 Co 0.1 Mn 0.1 O2 modified by a composite layer coating, and the specific preparation method includes the following steps:

[0047] S1. Weigh cerium powder with a purity of 99.9%, yttrium powder with a purity of 98.9%, iron powder with a purity of 99.7%, cobalt powder with a purity of 99.9%, and arsenic powder with a purity of 99.1% according to the elemental stoichiometric ratio of Ce:Y:Fe:Co:As being 0.12:0.28:1.2:2.8:12, and ball mill for 2 h at a speed of 500 r / min to obtain composite material I with a median particle size of 100 nm;

[0048] S2. Weigh composite material I and single-crystalline ternary cathode precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2 at a mass ratio of 1:1000, and stir and mix for 2 h at a speed of 200 r / min; place the mixed material in a spark plasma sintering furnace, sinter at 500 K, a sintering pressure of 5 MPa, and hold for 25 min to obtain Ce 0.12 Y 0.28 Fe 1.2 Co 2.8 As 12 coated Ni 0.8 Co 0.1 Mn 0.1 (OH)2, named modified precursor II, where the thickness of the Ce 0.12 Y 0.28 Fe 1.2 Co 2.8 As 12 coating layer is 5 nm;

[0049] S3. Weigh the modified precursor II and lithium carbonate according to the mass ratio of 2.54:1, stir and mix them at a speed of 500 r / min for 30 min, then place them in a roller hearth kiln. Under an oxygen atmosphere, keep them at 900 °C for 10 h to obtain the sintered material III;

[0050] S4. Crush the sintered material III with a jaw crusher to obtain a crushed material with a median particle size of 1 mm, then put it into a stone mortar mill, adjust the gap between the upper and lower grinding discs to 100 μm, and carry out the first grinding for 15 min to collect the material after the first grinding; then adjust the gap between the upper and lower grinding discs to 50 μm, put the material after the first grinding into it and carry out the second grinding for 5 min to obtain a spherical secondary ground material with an aspect ratio of 1.9:1, that is, the crushed material IV;

[0051] S5. Weigh 4-((6-hydroxyhexyl)oxy)phenyl 4-((6-hydroxyhexyl)oxy)benzoate, trimethylolpropane polyethylene glycol monomethyl ether, and the crushed material IV according to the mass ratio of 1:2.4:160, stir and mix them at a speed of 200 r / min for 10 min to prepare the mixture V;

[0052] S6. Preheat the internal temperature of the crushing cavity of the honeycomb mill to 95 °C, uniformly input the mixture V at a speed of 40 kg / h, and at the same time, introduce a mixed gas with a volume ratio of isophorone diisocyanate heated to 260 °C to nitrogen of 1:2000 at a flow rate of 40 m 3 / h, control the main engine speed to 2000 r / min for crushing, and obtain a liquid crystal polyurethane / Ce 0.12 Y 0.28 Fe 1.2 Co 2.8 As 12 composite layer-coated modified single-crystalline ternary cathode material. The obtained modified single-crystalline ternary cathode material is continuously conveyed to the trap under the action of the fan suction, and finally collected by the trap.

[0053] Example 3

[0054] The modified single-crystalline ternary cathode material in this example is a liquid crystal polyurethane / Ce 0.12 Y 0.28 Fe1Co3Sb 12 composite layer-coated modified single-crystalline cathode material LiNi 0.75 Co 0.1 Mn 0.15 O2, and the specific preparation method includes the following steps:

[0055] S1. Weigh cerium powder with a purity of 99.2%, yttrium powder with a purity of 99.9%, iron powder with a purity of 98.9%, cobalt powder with a purity of 98.9%, and antimony powder with a purity of 99.9% respectively according to the elemental stoichiometric ratio of Ce:Y:Fe:Co:Sb being 0.12:0.28:1:3:12, and ball-mill them at a rotation speed of 800 r / min for 2 h to obtain composite material I with a median particle size of 100 nm;

[0056] S2. Then weigh composite material I and single-crystalline ternary cathode precursor Ni 0.75 Co 0.1 Mn 0.15 (OH)2 according to a mass ratio of 1:900, and stir and mix them at a rotation speed of 400 r / min for 1 h; place the mixed material in a spark plasma sintering furnace, and sinter it at 800 K, a sintering pressure of 10 MPa, and hold for 10 min to obtain Ce 0.12 Y 0.28 Fe1Co3Sb 12 coated with Ni 0.75 Co 0.1 Mn 0.15 (OH)2, named modified precursor II, where the thickness of the Ce 0.12 Y 0.28 Fe1Co3Sb 12 coating layer is 5 nm;

[0057] S3. Weigh modified precursor II and lithium hexafluorophosphate according to a mass ratio of 2.2:1, stir and mix them at a rotation speed of 200 r / min for 40 min, and then place them in a roller hearth kiln. Under an oxygen atmosphere, hold at 900 °C for 14 h to obtain sintered material III;

[0058] S4. Crush sintered material III with a pair-roll crusher to obtain crushed material with a median particle size of 2 mm, and then put it into a stone mortar mill. Adjust the gap between the upper and lower grinding discs to 100 μm, and conduct primary grinding for 10 min to collect the material after primary grinding; then adjust the gap between the upper and lower grinding discs to 40 μm, put the material after primary grinding for secondary grinding for 10 min to obtain the material after secondary grinding with a spherical microstructure, that is, crushed material IV;

[0059] S5. Weigh 4-((6-hydroxyhexyl)oxy)phenyl 4-((6-hydroxyhexyl)oxy)benzoate, trimethylolpropane polyethylene glycol monomethyl ether, and crushed material IV according to a mass ratio of 1:1.2:50, and stir and mix them at a rotation speed of 200 r / min for 30 min to obtain mixture V;

[0060] S6. Preheat the internal temperature of the honeycomb mill crushing cavity to 60 °C, uniformly input mixture V at a speed of 30 kg / h, and at the same time input 3The flow rate of / h is introduced into a mixture of toluene diisocyanate heated to 280 °C and nitrogen with a volume ratio of 1:1800, and the main engine speed is controlled at 2400 r / min for grinding to obtain liquid crystal polyurethane / Ce with a median particle size of 3.5 μm 0.12 Y 0.28 Fe1Co3Sb 12 The composite layer-coated modified single-crystalline ternary cathode material. The obtained modified single-crystalline ternary cathode material is continuously transported to the trap under the action of the fan suction and finally collected by the trap

[0061] Example 4

[0062] The modified single-crystalline ternary cathode material in this example is liquid crystal polyurethane / Ce with a thickness of 30 nm 0.28 Y 0.12 Fe3Co1Sb 12 The single-crystalline cathode material LiNi 0.85 Co 0.05 Mn 0.1 O2, and the specific preparation method includes the following steps

[0063] S1. Weigh cerium powder with a purity of 99.2%, yttrium powder with a purity of 99.1%, iron powder with a purity of 99.9%, cobalt powder with a purity of 99.9%, and antimony powder with a purity of 98.9% according to the elemental stoichiometric ratio of Ce:Y:Fe:Co:Sb of 0.28:0.12:3:1:12, and ball-mill at a speed of 600 r / min for 4 h to obtain composite material I with a median particle size of 200 nm

[0064] S2. Weigh composite material I and single-crystalline ternary cathode precursor Ni 0.85 Co 0.05 Mn 0.1 (OH)2 at a mass ratio of 1:600, and stir and mix at a speed of 600 r / min for 2 h; place the mixed material in a spark plasma sintering furnace, sinter at 1000 K, sintering pressure of 9 MPa, and hold for 20 min to prepare Ce 0.28 Y 0.12 Fe3Co1Sb 12 coated Ni 0.85 Co 0.05 Mn 0.1 (OH)2, named modified precursor II, where Ce 0.28 Y 0.12 Fe3Co1Sb 12 The thickness of the coating layer is 8 nm

[0065] S3. Weigh the modified precursor II and lithium perchlorate according to a mass ratio of 2.4:1, stir and mix them at a rotation speed of 400 r / min for 50 min, then place them in a roller hearth kiln. Under an oxygen atmosphere, keep them at 850 °C for 15 h to obtain sintered material III.

[0066] S4. Crush the sintered material III with a pair-roll crusher to obtain crushed material with a median particle size of 2 mm, then put it into a stone mortar mill. Adjust the gap between the upper and lower grinding discs to 200 μm, conduct primary grinding for 15 min, and collect the material after primary grinding. Then adjust the gap between the upper and lower grinding discs to 50 μm, put the material after primary grinding for secondary grinding for 10 min to obtain spherical secondary ground material with an aspect ratio of 1.5:1, that is, crushed material IV.

[0067] S5. Weigh 4-((6-hydroxyhexyl)oxy)phenyl 4-((6-hydroxyhexyl)oxy)benzoate, trimethylolpropane polyethylene glycol monomethyl ether, and crushed material IV according to a mass ratio of 1:1.2:100, stir and mix them at a rotation speed of 200 r / min for 20 min to prepare mixture V.

[0068] S6. Preheat the internal temperature of the honeycomb mill crushing cavity to 80 °C, uniformly input mixture V at a rate of 25 kg / h, and at the same time, introduce a mixture of toluene diisocyanate heated to 280 °C and nitrogen with a volume ratio of 1:1800 at a flow rate of 80 m 3 / h. Control the main machine rotation speed to 1800 r / min for crushing to obtain a liquid crystal polyurethane / Ce 0.28 Y 0.12 Fe3Co1Sb 12 composite layer-coated modified single-crystalline ternary cathode material. The obtained modified single-crystalline ternary cathode material is continuously transported to the trap under the action of the fan suction and finally collected by the trap.

[0069] Example 5

[0070] The modified single-crystalline ternary cathode material in this example is a liquid crystal polyurethane / Ce 0.22 Y 0.18 Fe3Co1P 12 composite layer-coated modified single-crystalline cathode material LiNi 0.75 Co 0.1 Mn 0.15 O2, and the specific preparation method includes the following steps:

[0071] S1. Weigh cerium powder with a purity of 99.2%, yttrium powder with a purity of 98.9%, iron powder with a purity of 99.7%, cobalt powder with a purity of 98.9%, and phosphorus powder with a purity of 99.4% respectively according to the element stoichiometric ratio of Ce:Y:Fe:Co:P being 0.22:0.18:3:1:12, and ball-mill them at a rotation speed of 600 r / min for 3 h to obtain composite material I with a median particle size of 400 nm;

[0072] S2. Weigh composite material I and single-crystalline ternary cathode precursor Ni 0.75 Co 0.1 Mn 0.15 (OH)2 according to a mass ratio of 1:800, and stir and mix them at a rotation speed of 200 r / min for 1.5 h; Place the mixed material in a spark plasma sintering furnace, and sinter it at 600 K, a sintering pressure of 8 MPa, and keep the temperature for 15 min to obtain Ce 0.22 Y 0.18 Fe3Co1P 12 coated with Ni 0.75 Co 0.1 Mn 0.15 (OH)2, named modified precursor II, where the thickness of the Ce 0.22 Y 0.18 Fe3Co1P 12 coating layer is 10 nm;

[0073] S3. Weigh modified precursor II and lithium carbonate according to a mass ratio of 2.12:1, stir and mix them at a rotation speed of 300 r / min for 50 min, and then place them in a roller hearth kiln. Under an oxygen atmosphere, keep the temperature at 900 °C for 12 h to obtain sintered material III;

[0074] S4. Crush sintered material III with a rotary wheel mill to obtain crushed material with a median particle size of 2 mm, and then put it into a stone mortar mill. Adjust the gap between the upper and lower grinding discs to 150 μm, and conduct primary grinding for 15 min to collect the material after primary grinding; Then adjust the gap between the upper and lower grinding discs to 30 μm, put the material after primary grinding, and conduct secondary grinding for 5 min to obtain spherical secondary ground material with an aspect ratio of 1.2:1, that is, crushed material IV;

[0075] S5. Weigh 4-((6-hydroxyhexyl)oxy)phenyl 4-((6-hydroxyhexyl)oxy)benzoate, trimethylolpropane polyethylene glycol monomethyl ether, and crushed material IV according to a mass ratio of 1:2.0:100, and stir and mix them at a rotation speed of 150 r / min for 40 min to obtain mixture V;

[0076] S6. Preheat the internal temperature of the honeycomb mill crushing cavity to 60 °C, uniformly input mixture V at a speed of 40 kg / h, and at the same time press 90 m 3The flow rate of / h is introduced into a mixture of isophorone diisocyanate heated to 300 °C and nitrogen with a volume ratio of 1:1600. The main engine speed is controlled at 1800 r / min for pulverization to obtain liquid crystal polyurethane / Ce with a median particle size of 4 μm 0.22 Y 0.18 Fe3Co1P 12 The composite layer-coated modified single-crystalline ternary cathode material. The obtained modified single-crystalline ternary cathode material is continuously transported to the trap under the action of the fan suction and finally collected by the trap

[0077] Example 6

[0078] The modified single-crystalline ternary cathode material in this example is liquid crystal polymer / Ce with a thickness of 35 nm 0.1 Y 0.3 Fe1Co3Sb 12 Coated modified single-crystalline cathode material LiNi 0.75 Co 0.1 Mn 0.15 O2, and the specific preparation steps are as follows

[0079] S1. Weigh cerium powder with a purity of 99%, yttrium powder with a purity of 99%, iron powder with a purity of 99.7%, cobalt powder with a purity of 99%, and antimony powder with a purity of 99.1% according to the elemental stoichiometric ratio of Ce:Y:Fe:Co:Sb of 0.1:0.3:1:3:12, and ball mill at a speed of 600 r / min for 3 h to obtain composite material I with a median particle size of 300 nm

[0080] S2. Then weigh composite material I and single-crystalline ternary cathode precursor Ni 0.75 Co 0.1 Mn 0.15 (OH)2 at a mass ratio of 1:800 and stir and mix at a speed of 400 r / min for 1.5 h; place the mixed material in a spark plasma sintering furnace, sinter at 900 K, sintering pressure of 7 MPa, and hold for 15 min to prepare Ce 0.1 Y 0.3 Fe1Co3Sb 12 Coated Ni 0.75 Co 0.1 Mn 0.15 (OH)2, named modified precursor II, where the thickness of the Ce 0.1 Y 0.3 Fe1Co3Sb 12 coating layer is 9 nm

[0081] S3. Weigh the modified precursor II and lithium perchlorate according to a mass ratio of 2.36:1, stir and mix them at a rotation speed of 350 r / min for 45 min, and then place them in a roller hearth furnace. Under an oxygen atmosphere, keep them at 880 °C for 19 h to obtain the sintered material III;

[0082] S4. Crush the sintered material III with a rotary wheel mill to obtain a crushed material with a median particle size of 2.5 mm, and then put it into a stone mortar mill. Adjust the gap between the upper and lower grinding discs to 150 μm, and conduct the first grinding for 15 min to collect the material after the first grinding; then adjust the gap between the upper and lower grinding discs to 35 μm, put the material after the first grinding and conduct the second grinding for 8 min to obtain a spherical secondary ground material with an aspect ratio of 1.5:1, that is, the crushed material IV;

[0083] S5. Weigh 4-((6-hydroxyhexyl)oxy)phenyl 4-((6-hydroxyhexyl)oxy)benzoate, trimethylolpropane polyethylene glycol monomethyl ether, and the crushed material IV according to a mass ratio of 1:1.8:120, stir and mix them at a rotation speed of 140 r / min for 15 min to prepare the mixture V;

[0084] S6. Preheat the internal temperature of the honeycomb mill crushing cavity to 85 °C, uniformly input the mixture V at a rate of 22 kg / h, and at the same time, introduce a mixed gas of hexamethylene diisocyanate heated to 285 °C and nitrogen with a volume ratio of 1:1850 at a flow rate of 70 m 3 / h. Control the main machine rotation speed to 2200 r / min. After crushing, obtain a liquid crystal polyurethane / Ce 0.1 Y 0.3 Fe1Co3Sb 12 composite layer-coated modified single-crystalline ternary cathode material. The obtained modified single-crystalline ternary cathode material is continuously transported to the trap under the action of the fan suction, and finally collected by the trap.

[0085] Example 7

[0086] The modified single-crystalline ternary cathode material in this example is a liquid crystal polyurethane / Ce with a thickness of 40 nm 0.15 Y 0.25 Fe2Co2As 12 coated modified single-crystalline cathode material LiNi 0.9 Co 0.05 Mn 0.05 O2, and the specific preparation steps are as follows:

[0087] S1. Weigh cerium powder with a purity of 99.4%, yttrium powder with a purity of 99.2%, iron powder with a purity of 99%, cobalt powder with a purity of 99.6% and arsenic powder with a purity of 99.1% according to the elemental stoichiometric ratio of Ce:Y:Fe:Co:As being 0.15:0.25:2:2:12 respectively, and ball-mill them at a rotation speed of 600 r / min for 3 h to obtain composite material I with a median particle size of 350 nm;

[0088] S2. Then weigh composite material I and single-crystalline ternary cathode precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)2 according to a mass ratio of 1:800, and stir and mix them at a rotation speed of 400 r / min for 1.5 h; Place the mixed material in a spark plasma sintering furnace, sinter at 850 K with a sintering pressure of 6 MPa and hold for 15 min to obtain Ce 0.15 Y 0.25 Fe2Co2As 12 coated with Ni 0.9 Co 0.05 Mn 0.05 (OH)2, named modified precursor II, where the thickness of the Ce 0.15 Y 0.25 Fe2Co2As 12 coating layer is 6 nm;

[0089] S3. Weigh modified precursor II and lithium perchlorate according to a mass ratio of 2.52:1, stir and mix them at a rotation speed of 350 r / min for 45 min, and then place them in a roller hearth kiln. Under an oxygen atmosphere, hold at 880 °C for 19 h to obtain sintered material III;

[0090] S4. Crush sintered material III with a rotary wheel mill to obtain crushed material with a median particle size of 2.5 mm, then put it into a stone mortar mill, adjust the gap between the upper and lower grinding discs to 300 μm, and conduct primary grinding for 12 min to collect the material after primary grinding; Then adjust the gap between the upper and lower grinding discs to 45 μm, put the material after primary grinding for secondary grinding for 10 min to obtain spherical secondary grinding material with an aspect ratio of 1.7:1, that is, crushed material IV;

[0091] S5. Weigh 4-((6-hydroxyhexyl)oxy)phenyl 4-((6-hydroxyhexyl)oxy)benzoate, trimethylolpropane polyethylene glycol monomethyl ether, and crushed material IV according to a mass ratio of 1:1.8:120, and stir and mix them at a rotation speed of 200 r / min for 15 min to obtain mixture V;

[0092] S6. Preheat the internal temperature of the honeycomb mill crushing cavity to 72 °C, uniformly input mixture V at a speed of 36 kg / h and simultaneously at 82 m 3The flow rate of / h is introduced into a mixture of hexamethylene diisocyanate heated to 285 °C and nitrogen with a volume ratio of 1:1900. The main engine speed is controlled at 2100 r / min. After pulverization, liquid crystal polyurethane / Ce with a median particle size of 4.2 μm is obtained. 0.15 Y 0.25 Fe2Co2As 12 The modified single-crystalline ternary cathode material with a composite layer coating is obtained. The obtained modified single-crystalline ternary cathode material is continuously transported to the trap under the action of the fan suction and finally collected by the trap.

[0093] Comparative Example 1

[0094] In this comparative example, the unmodified single-crystalline ternary cathode material is LiNi 0.7 Co 0.1 Mn 0.2 O2, and its preparation method is the same as that of Example 1, except that the liquid crystal polyurethane / Ce 0.12 Y 0.28 Fe2Co2Sb 12 coating modification is not carried out. The specific steps of the preparation method are as follows:

[0095] Weigh the single-crystalline ternary precursor Ni 0.7 Co 0.1 Mn 0.2 (OH)2 and lithium hydroxide according to a mass ratio of 2.12:1, stir and mix at a speed of 500 r / min for 60 min, then place it in a roller hearth kiln. Under an oxygen atmosphere, keep it at 800 °C for 20 h to obtain a sintered material; pulverize and screen the sintered material to obtain a single-crystalline cathode material LiNi with a median particle size of 4 μm 0.7 Co 0.1 Mn 0.1 O2.

[0096] Comparative Example 2

[0097] The single-crystalline ternary cathode material in this comparative example is Ce 0.12 Y 0.28 Fe 1.2 Co 2.8 As 12 The single-crystalline cathode material LiNi with a Ce 0.8 Co 0.1 Mn 0.1 O2 with a composite layer coating, and the specific preparation steps are as follows:

[0098] S1. Weigh cerium powder with a purity of 99.9%, yttrium powder with a purity of 98.9%, iron powder with a purity of 99.7%, cobalt powder with a purity of 99.9% and arsenic powder with a purity of 99.1% according to the elemental stoichiometric ratio of Ce:Y:Fe:Co:As being 0.12:0.28:1.2:2.8:12 respectively, and ball-mill them at a rotation speed of 500 r / min for 2 h to obtain composite material I with a median particle size of 100 nm;

[0099] S2. Weigh composite material I and single-crystalline ternary cathode precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2 according to a mass ratio of 1:1000, and stir and mix them at a rotation speed of 200 r / min for 2 h; Place the mixed material in a spark plasma sintering furnace, sinter at 500 K with a sintering pressure of 5 Pa for 25 min to prepare Ce 0.12 Y 0.28 Fe 1.2 Co 2.8 As 12 coated Ni 0.8 Co 0.1 Mn 0.1 (OH)2, named modified precursor II, where the thickness of the coating layer of Ce 0.12 Y 0.28 Fe 1.2 Co 2.8 As 12 is 5 nm;

[0100] S3. Weigh modified precursor II and lithium carbonate according to a mass ratio of 2.54:1, stir and mix them at a rotation speed of 500 r / min for 30 min, and then place them in a roller hearth kiln. Under an oxygen atmosphere, keep them at 900 °C for 10 h to obtain sintered material III;

[0101] S4. Crush sintered material III with a jaw crusher to obtain crushed material with a median particle size of 1 mm, then put it into a stone mortar mill, adjust the gap between the upper and lower grinding discs to 100 μm, and conduct primary grinding for 15 min to collect the material after primary grinding; Then adjust the gap between the upper and lower grinding discs to 50 μm, put the material after primary grinding for secondary grinding for 5 min to obtain spherical secondary ground material with an aspect ratio of 1.9:1, that is, crushed material IV;

[0102] S5. Feed crushed material IV into the honeycomb mill cavity at a uniform speed of 40 kg / h, and at the same time, introduce nitrogen at a flow rate of 40 m 3 / h, adjust the main engine speed to 2000 r / min for crushing to obtain single-crystalline ternary cathode material with a median particle size of 5.0 μm. The obtained single-crystalline cathode material is continuously transported to the trap under the action of the blower suction, and finally collected by the trap.

[0103] Comparative Example 3

[0104] The single-crystalline ternary cathode material in this comparative example is a single-crystalline cathode material LiNi coated and modified with liquid crystal polyurethane 0.75 Co 0.1 Mn 0.15 O2, and the specific preparation steps are as follows:

[0105] S1. Weigh the single-crystalline ternary precursor Ni 0.75 Co 0.1 Mn 0.15 (OH)2 and lithium hexafluorophosphate according to a mass ratio of 2.2:1, stir and mix them at a speed of 200 r / min for 40 min, then place them in a roller hearth furnace, and keep them at 900 °C for 14 h in an oxygen atmosphere to obtain a sintered material;

[0106] S2. Crush and screen the sintered material to obtain a crushed material with a median particle size of 3 μm; then weigh 4-((6-hydroxyhexyl)oxy)phenyl 4-((6-hydroxyhexyl)oxy)benzoate, trimethylolpropane polyethylene glycol monomethyl ether, toluene diisocyanate, and the crushed material according to a mass ratio of 1:1.2:1.04:50, stir and mix them at a speed of 200 r / min for 30 min, and place the mixed material in a vacuum oven for thermal polymerization at 110 °C for 4 h to prepare the single-crystalline ternary cathode material.

[0107] Comparative Example 4

[0108] This comparative example of ternary material LiNi 0.85 Co 0.05 Mn 0.1 O2 was prepared by referring to the method described in Example 1 of the Chinese patent application document with the publication number CN112864369A in the prior art.

[0109] Test Example

[0110] The single-crystalline ternary cathode materials in the examples and comparative examples were used as the cathode materials respectively, a battery-grade lithium sheet was used as the anode material, and an electrolyte with lithium hexafluorophosphate as the main component was used to assemble a simulated battery, and relevant performance tests were carried out; at 50 °C and within a cut-off voltage range of 3.0 - 4.7 V, cyclic charge and discharge were carried out at a 1C rate, and the average values of the charging and discharging voltages in the 10th week, 20th week, 30th week... up to the 200th week were recorded and calculated, and were denoted as CH1 - CH20 and DIS1 - DIS20 respectively; the formula: was used to calculate the DCR value, where X = 1, 2, 3... 20.

[0111] Data and Analysis

[0112] Table 1

[0113]

[0114]

[0115] It can be seen from the calculation results in Table 1 that compared with the single-crystalline cathode material prepared in the comparative example, the DCR growth rate of the modified single-crystalline ternary cathode material obtained in the example is lower. At the same time, combined with Figure 1 the curve in, it can also be seen that the DCR growth rate of Example 1 is between -5% and 5%, and the value is much smaller than that of Comparative Example 1. Figure 2 and Figure 3 are respectively the microscopic morphology test diagrams of the cathode materials prepared in Example 1 and Comparative Example 1. The microscopic morphology test was carried out by field emission scanning electron microscopy to take the morphology at the same magnification. From Figure 2 and Figure 3 it can be seen that in Example 1, the coating of the single-crystalline ternary cathode material by the dynamically coated liquid crystal polyurethane / Ce 0.12 Y 0.28 Fe2Co2Sb 12 composite layer is more uniform and effective.

[0116] The above test results show that through the coating of the liquid crystal polyurethane / Ce x Y 0.4-x Fe y Co 4-y M 12 composite layer, the generation of non-active Ni ions in the single-crystalline ternary cathode material and the escape of oxygen during the process of lithium extraction can be inhibited, the increase of the DCR value of the battery assembled at high temperature and high cut-off voltage is reduced, and the cycle stability of the battery is effectively improved.

[0117] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A modified single-crystalline ternary cathode material, characterized in that: It includes a matrix material and a coating material coated on the surface of the matrix material; the matrix material is a single-crystalline ternary cathode material LiNi a Co b Mn 1-a-b O2, where 0.7 ≤ a < 1, 0 < b < 0.2, and 1 - a - b > 0; the coating material includes liquid crystal polyurethane / Ce x Y 0.4-x Fe y Co 4-y M 12 composite layer, where 0.1 ≤ x < 0.4, 0 < y < 4, and M is selected from at least one of the elements Sb, P, and As; the Ce x Y 0.4- x Fe y Co 4-y M 12 effectively inhibits the crystallinity of the generated liquid crystal polyurethane.

2. The modified single-crystalline ternary cathode material according to claim 1, wherein: The thickness of the coating material is 25 - 50 nm.

3. A method for preparing the modified single-crystalline ternary cathode material according to claim 1 or 2, characterized in that: It includes the following steps: S1. Using cerium powder, yttrium powder, iron powder, cobalt powder, and M powder as the initial raw materials, weighing them according to the elemental stoichiometric ratio of Ce:Y:Fe:Co:M as x:0.4 - x:y:4 - y:12, and obtaining a composite material after ball milling; S2. Mix the composite material prepared in S1 with the single-crystalline ternary cathode precursor Ni a Co b Mn 1-a-b (OH)2 by stirring, and then place the mixed material in a spark plasma sintering furnace for heat preservation sintering to obtain a modified precursor, i.e., Ce x Y 0.4-x Fe y Co 4-y M 12 coated with Ni a Co b Mn 1-a-b (OH)2; S3. Stirring and mixing the modified precursor prepared in S2 with a lithium source, and sintering in an oxygen atmosphere to obtain a sintered material; S4. Crushing the sintered material obtained in S3 and then grinding it to obtain a crushed material with a spherical and / or spherical-like microstructure; S5. Stirring and mixing a hydroxy liquid crystal monomer, trimethylolpropane polyethylene glycol monomethyl ether, and the crushed material obtained in S4 to obtain a mixed material; S6. Keeping the temperature of the honeycomb mill crushing cavity, adjusting the main machine speed, adding the mixed material obtained in S5, and introducing a mixed gas. After crushing, the modified single-crystalline ternary cathode material is obtained, where the mixed gas is a mixture of heated isocyanate and nitrogen; Among them, in S1 and S2, 0.1 ≤ x < 0.4, 0 < y < 4, and M is selected from at least one of Sb, P, and As elements; in S2, 0.7 ≤ a < 1, 0 < b < 0.2, and 1 - a - b > 0.

4. The preparation method of the modified single-crystalline ternary cathode material according to claim 3, wherein: In S1, the rotation speed of the ball milling is 500 - 900 r / min, the time is 2 - 4 h, and the median particle size of the composite material is 100 - 500 nm; in S2, during the stirring and mixing process, the rotation speed is 200 - 800 r / min, and the mixing time is 1 - 2 h; in S3, during the stirring and mixing process, the rotation speed is 200 - 500 r / min, and the mixing time is 30 - 60 min; in S5, during the stirring and mixing process, the rotation speed is 100 - 200 r / min, and the mixing time is 10 - 40 min.

5. The preparation method of the modified single-crystalline ternary cathode material according to claim 3, characterized in that: In S2, the mass ratio of the composite material to the single-crystalline ternary cathode precursor Ni a Co b Mn 1-a-b (OH)2 is 1:500 to 1000; for the modified precursor Ce x Y 0.4-x Fe y Co 4-y M 12 coating Ni a Co b Mn 1-a-b (OH)2, the thickness of Ce x Y 0.4-x Fe y Co 4-y M 12 is 5 to 10 nm; in S3, the mass ratio of the modified precursor to the lithium source is 2.12 to 2.54:1; in S5, the mass ratio of the hydroxy liquid crystal monomer, trimethylolpropane polyethylene glycol monomethyl ether, and crushed material is 1:1.2 to 2.4:50 to 160.

6. The preparation method of the modified single-crystalline ternary cathode material according to claim 3, wherein: In S2, during the heat preservation and sintering process, the temperature is 500 - 1000 K, the sintering pressure is 5 - 10 MPa, and the time is 10 - 25 min; in S3, the sintering temperature is 800 - 900 °C, and the time is 10 - 20 h.

7. The preparation method of the modified single-crystalline ternary cathode material according to claim 3, wherein: In S4, after crushing the sintered material, it is put into a stone mortar mill, the gap between the upper and lower grinding disks is adjusted to 100 - 300 μm, and it is ground once. The material after the first grinding is collected; then the gap between the upper and lower grinding disks is adjusted to 20 - 50 μm, and the material after the first grinding is put in for secondary grinding to obtain a secondary ground material with a spherical and / or spherical-like shape with an aspect ratio of major axis to minor axis of 1.2 - 1.9:1, that is, the crushed material.

8. The preparation method of the modified single-crystalline ternary cathode material according to claim 3, wherein: In S6, the temperature inside the honeycomb mill's pulverizing cavity is maintained at 60 - 95 °C, and the main machine speed of the honeycomb mill is 1600 - 2400 r / min; the mixture and the mixed gas are synchronously input into the pulverizing cavity of the honeycomb mill, where the input speed of the mixture is 20 - 40 kg / h, and the flow rate of the mixed gas passing through is 40 - 120 m 3 / h; the mixed gas is a mixture of isocyanate heated to 260 - 300 °C and nitrogen; the volume ratio of isocyanate to nitrogen in the mixed gas is 1:1500 - 2000.

9. The preparation method of the modified single-crystalline ternary cathode material according to any one of claims 3 to 8, characterized in that: In S3, the lithium source is at least one of lithium hydroxide, lithium carbonate, lithium hexafluorophosphate, and lithium perchlorate; in S5, the hydroxy liquid crystal monomer is 4 - ((6 - hydroxyhexyl)oxy)phenyl 4 - ((6 - hydroxyhexyl)oxy)benzoate; in S6, the isocyanate is a diisocyanate, and the diisocyanate is at least one of hexamethylene diisocyanate, toluene diisocyanate, and isophorone diisocyanate; in S6, the median particle size of the modified single-crystalline ternary cathode material is 2 - 5 μm.

10. A lithium-ion battery, characterized in that, It includes a positive electrode, a negative electrode, a separator, and an electrolyte, and the positive electrode contains the modified single-crystalline ternary cathode material as described in claim 1 or 2.

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