Preparation method of carbon nanotube coated single crystal layered oxide positive electrode material

Abstract

The invention discloses a preparation method of a carbon nanotube coated single crystal layered oxide positive electrode material, and relates to the technical field of battery positive electrode materials. The specific preparation method comprises the following steps: firstly, adding alkali, sodium salt, ferric salt, manganese salt, magnesium salt, calcium salt and an amino compound into a solvent, stirring to obtain a mixed solution, carrying out spray drying and air jet pulverization on the mixed solution, and finally, heating and preserving heat under a nitrogen condition to obtain the carbon nanotube coated single crystal layered oxide positive electrode material. According to the preparation method disclosed by the invention, the carbon nanotubes are grown inside and on the surface of the single-crystal layered oxide positive electrode material in situ, so that the intrinsic conductivity of the single-crystal layered oxide positive electrode material is improved, and the positive electrode material with high rate, high capacity and good cycle performance is finally obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of cathode materials for batteries, and particularly to a preparation method of a carbon nanotube-coated single-crystal layered oxide cathode material. Background Art

[0002] In recent years, with the continuous progress of battery technology and the increasing shortage of resources, sodium-ion batteries have attracted much attention due to their rich resources and low cost, and are regarded as important alternatives to lithium-ion batteries. Among various types of cathode materials for sodium-ion batteries, layered oxide cathode materials have become a current research hotspot because of their simple synthesis, excellent performance, especially high capacity and good electrochemical performance. However, the fast charging performance of such cathode materials still needs to be improved to meet broader application requirements. Among them, single-crystal layered oxide cathode materials are considered a potential solution because of their high structural stability and fewer grain boundaries, showing good cycle stability and lower interfacial side reactions. However, currently, single-crystal layered oxide cathode materials for sodium-ion batteries generally have the defect of poor rate performance, that is, under high-current charge and discharge conditions, the battery capacity decays rapidly, which limits their application in high-power batteries.

[0003] Currently, methods such as adjusting the material composition and optimizing the preparation process have been used to reduce the synthesis difficulty of single-crystal layered oxide cathode materials and improve their fast charging performance and rate performance. However, these methods still have certain limitations and deficiencies in practical applications and need further research and improvement. Therefore, developing single-crystal layered oxide cathode materials with excellent fast charging performance and rate performance remains an important research direction in the field of cathode materials for sodium-ion batteries. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method of a carbon nanotube-coated single-crystal layered oxide cathode material to solve problems such as poor performance of existing single-crystal layered oxide cathode materials.

[0005] To solve the above technical problems, the present invention specifically provides the following technical solutions: The present invention discloses a preparation method of a carbon nanotube-coated single-crystal layered oxide cathode material, including: Adding an alkali, a sodium salt, an iron salt, a manganese salt, a magnesium salt, a calcium salt, and an amino compound into a solvent and stirring to obtain a mixed solution. The mixed solution is subjected to spray drying and airflow pulverization to obtain a pulverized dry powder precursor, and the pulverized dry powder precursor is subjected to high-temperature carbonization under nitrogen conditions to obtain a carbon nanotube-coated single-crystal layered oxide cathode material; the mass ratio of the usage amount of the sodium salt to the amino compound is 1:2 - 16.

[0006] Preferably, the base is sodium hydroxide, the sodium salt is at least one of sodium carbonate, sodium bicarbonate, sodium sulfate, sodium nitrate, sodium chloride and sodium oxalate, and the mass ratio of the usage amount of the base to the sodium salt is 1:0.1 - 0.3.

[0007] Preferably, the iron salt is at least one of ferrous oxalate, iron nitrate, ferrous acetate, ferrous sulfate, ferrous acetate and ferrous chloride, and the mass ratio of the usage amount of the sodium salt to the iron salt is 1:10 - 13.

[0008] Preferably, the manganese salt is at least one of manganese nitrate, manganese chloride, manganese oxalate, manganese acetate, manganese sulfate and manganese acetylacetonate, and the mass ratio of the usage amount of the sodium salt to the manganese salt is 1:5 - 7.

[0009] Preferably, the magnesium salt is at least one of magnesium nitrate, magnesium acetate, magnesium chloride, magnesium sulfate and magnesium oxalate, and the mass ratio of the usage amount of the sodium salt to the magnesium salt is 1:0.5 - 1.2.

[0010] Preferably, the calcium salt is at least one of calcium nitrate, calcium sulfate, calcium chloride, calcium oxalate and calcium acetate, and the mass ratio of the usage amount of the sodium salt to the calcium salt is 1:0.6 - 1.2.

[0011] Preferably, the amino compound is at least one of urea, thiourea, melamine, 2 - aminoethylsulfonamide, 2 - pyrazol - 1 - ylethylamine, triethylenediamine, cyclohexeneimine and isopropanolamine. The mass ratio of the usage amount of urea to 2 - aminoethylsulfonamide is 1:0.2 - 0.4, and the mass ratio of the usage amount of urea to 2 - pyrazol - 1 - ylethylamine is 1:0.2 - 0.4. Urea, 2 - aminoethylsulfonamide and 2 - pyrazol - 1 - ylethylamine can be in - situ catalytically grown on the surface of the single - crystal layered oxide to generate carbon nanotubes, which are more uniformly and tightly coated on the single - crystal layered oxide, improving the electrical conductivity of the single - crystal layered oxide.

[0012] Preferably, the solvent is water, and the mass ratio of the usage amount of the amino compound to the solvent is 1:5 - 8.

[0013] Preferably, the inlet air temperature for spray drying is 160 - 200 °C, the feeding rate is 190 - 210 mL / h, the heating rate for high - temperature carbonization is 1.5 - 3 °C / min. First, it is heated to 300 - 400 °C and kept warm for 5 - 7 h, and then heated to 800 - 1000 °C and kept warm for 9 - 12 h.

[0014] The present invention also discloses the application of the carbon nanotube - coated single - crystal layered oxide cathode material prepared by any of the above - mentioned preparation methods in the preparation of a battery.

[0015] The present invention discloses a preparation method of a carbon nanotube - coated single - crystal layered oxide cathode material, comprising: An alkali, a sodium salt, an iron salt, a manganese salt, a magnesium salt, a calcium salt and an amino compound are added to a solvent and stirred to obtain a mixed solution. The mixed solution is spray-dried at an inlet air temperature of 160 - 200 °C and a feed rate of 190 - 210 mL / h, and then air-flow pulverized to obtain a pulverized dry powder precursor. The pulverized dry powder precursor is heated to 300 - 400 °C at a heating rate of 1.5 - 3 °C / min under nitrogen conditions and held for 5 - 7 h, and then heated to 800 - 1000 °C and held for 9 - 12 h to obtain a carbon nanotube-coated single-crystal layered oxide cathode material.

[0016] Preferably, the alkali is sodium hydroxide, and the sodium salt is at least one of sodium carbonate, sodium bicarbonate, sodium sulfate, sodium nitrate, sodium chloride and sodium oxalate.

[0017] Preferably, the mass ratio of the usage amounts of the alkali to the sodium salt is 1:0.1 - 0.3.

[0018] Preferably, the iron salt is at least one of ferrous oxalate, iron nitrate, ferrous acetate, ferrous sulfate, ferrous acetate and ferrous chloride.

[0019] Preferably, the mass ratio of the usage amounts of the sodium salt to the iron salt is 1:10 - 13.

[0020] Preferably, the manganese salt is at least one of manganese nitrate, manganese chloride, manganese oxalate, manganese acetate, manganese sulfate and manganese acetylacetonate.

[0021] Preferably, the mass ratio of the usage amounts of the sodium salt to the manganese salt is 1:5 - 7.

[0022] Preferably, the magnesium salt is at least one of magnesium nitrate, magnesium acetate, magnesium chloride, magnesium sulfate and magnesium oxalate.

[0023] Preferably, the mass ratio of the usage amounts of the sodium salt to the magnesium salt is 1:0.5 - 1.2.

[0024] Preferably, the calcium salt is at least one of calcium nitrate, calcium sulfate, calcium chloride, calcium oxalate and calcium acetate.

[0025] Preferably, the mass ratio of the usage amounts of the sodium salt to the calcium salt is 1:0.6 - 1.2.

[0026] Preferably, the amino compound is at least one of urea, thiourea, melamine, 2-aminoethylsulfonamide, 2-pyrazol-1-ylethylamine, triethylenediamine, cyclohexylimine and isopropanolamine.

[0027] More preferably, the mass ratio of the usage amounts of urea to 2-aminoethylsulfonamide is 1:0.2 - 0.4.

[0028] More preferably, the mass ratio of the usage amounts of urea to 2-pyrazol-1-ylethylamine is 1:0.2 - 0.4.

[0029] Preferably, the mass ratio of the usage amounts of the sodium salt to the amino compound is 1:2 - 16.

[0030] Preferably, the solvent is water, and the mass ratio of the usage amount of the amino compound to the solvent is 1:5 - 8.

[0031] More preferably, when preparing the carbon nanotube-coated single-crystalline layered oxide cathode material of the present invention, on the basis of using 2-aminoethylsulfonamide and 2-pyrazol-1-ylethylamine, 2-carboxyethylphenylphosphinic acid is used. The synergistic use of 2-carboxyethylphenylphosphinic acid to prepare the carbon nanotube-coated single-crystalline layered oxide cathode material can further provide more reactive sites, thereby improving the reversible capacity, rate performance, and cycling performance of the fabricated battery.

[0032] Preferably, the mass ratio of the usage amounts of 2-aminoethylsulfonamide to 2-carboxyethylphenylphosphinic acid is 1:0.1 - 0.3.

[0033] The present invention has the following beneficial effects compared with the prior art: The present invention provides a preparation method of a carbon nanotube-coated single-crystalline layered oxide cathode material. First, an alkali, a sodium salt, an iron salt, a manganese salt, a magnesium salt, a calcium salt, and an amino compound are added to a solvent and stirred to obtain a mixed solution. The mixed solution is subjected to spray drying and air jet milling, and finally, it is heated and kept warm under a nitrogen atmosphere to obtain the carbon nanotube-coated single-crystalline layered oxide cathode material. The preparation method of the present invention enables the in-situ growth of carbon nanotubes inside and on the surface of the single-crystalline layered oxide cathode material, improves the intrinsic conductivity of the single-crystalline layered oxide cathode material, and finally obtains a cathode material with high rate, high capacity, and good cycling performance, so as to be suitable for the application of fast-charging sodium-ion batteries in the small-power field. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only exemplary, and for those of ordinary skill in the art, without creative efforts, other implementation drawings can also be obtained according to the provided drawings.

[0035] Figure 1 It is a scanning electron microscope analysis diagram of the carbon nanotube-coated single-crystalline layered oxide cathode material. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0037] First, the concepts involved in the present application will be described below with reference to the accompanying drawings. It should be noted here that the descriptions of the following concepts are only for making the content of the present application easier to understand, and do not represent a limitation on the protection scope of the present application; at the same time, without conflict, the embodiments and the features in the embodiments in the present application can be combined with each other. The present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0038] The specific meanings of the abbreviations used in the specification and claims are as follows: Example 1: Preparation of carbon nanotube-coated single-crystalline layered oxide cathode material: Sodium hydroxide, sodium nitrate, iron nitrate, manganese nitrate, magnesium acetate, calcium acetate and urea were added to water and stirred to obtain a mixed solution. The mixed solution was spray-dried at an inlet air temperature of 180 °C and a feed rate of 200 mL / h to obtain a dry powder precursor, and the dry powder precursor was further pulverized by air flow to obtain a pulverized dry powder precursor. The pulverized dry powder precursor was heated to 350 °C at a heating rate of 2 °C / min under nitrogen conditions and held for 6 h, and then heated to 900 °C and held for 10 h to obtain the carbon nanotube-coated single-crystalline layered oxide cathode material. Among them, the mass ratio of the usage amounts of sodium hydroxide and sodium nitrate is 1:0.194, the mass ratio of the usage amounts of sodium nitrate and iron nitrate is 1:11.38, the mass ratio of the usage amounts of sodium nitrate and manganese nitrate is 1:5.76, the mass ratio of the usage amounts of sodium nitrate and magnesium acetate is 1:0.84, the mass ratio of the usage amounts of sodium nitrate and calcium acetate is 1:0.93, the mass ratio of the usage amounts of sodium nitrate and urea is 1:9.41, and the mass ratio of the usage amounts of urea and water is 1:5.81.

[0039] Example 2: Preparation of carbon nanotube-coated single-crystalline layered oxide cathode material: Compared with Example 1, the difference in this example is that the mass ratio of the usage amounts of sodium nitrate and urea is 1:3.53, and other conditions and parameters are the same as those in Example 1.

[0040] Example 3: Preparation of Carbon Nanotube-Coated Single-Crystalline Layered Oxide Cathode Material: Sodium hydroxide, sodium nitrate, ferric nitrate, manganese nitrate, magnesium acetate, calcium acetate, and melamine were added to water and stirred to obtain a mixed solution. The mixed solution was spray-dried at an inlet air temperature of 180 °C and a feed rate of 200 mL / h to obtain a dry powder precursor, and the dry powder precursor was further pulverized by air flow to obtain a pulverized dry powder precursor. The pulverized dry powder precursor was heated to 350 °C at a heating rate of 2 °C / min under nitrogen conditions and held for 6 h, and then heated to 900 °C and held for 10 h to obtain the carbon nanotube-coated single-crystalline layered oxide cathode material. The mass ratio of the usage amounts of sodium hydroxide to sodium nitrate was 1:0.194, the mass ratio of the usage amounts of sodium nitrate to ferric nitrate was 1:11.38, the mass ratio of the usage amounts of sodium nitrate to manganese nitrate was 1:5.76, the mass ratio of the usage amounts of sodium nitrate to magnesium acetate was 1:0.84, the mass ratio of the usage amounts of sodium nitrate to calcium acetate was 1:0.93, the mass ratio of the usage amounts of sodium nitrate to melamine was 1:7.06, and the mass ratio of the usage amounts of urea to water was 1:5.81.

[0041] Example 4: Preparation of Carbon Nanotube-Coated Single-Crystalline Layered Oxide Cathode Material: Sodium hydroxide, sodium nitrate, ferric nitrate, manganese nitrate, magnesium acetate, calcium acetate, and thiourea were added to water and stirred to obtain a mixed solution. The mixed solution was spray-dried at an inlet air temperature of 180 °C and a feed rate of 200 mL / h to obtain a dry powder precursor, and the dry powder precursor was further pulverized by air flow to obtain a pulverized dry powder precursor. The pulverized dry powder precursor was heated to 350 °C at a heating rate of 2 °C / min under nitrogen conditions and held for 6 h, and then heated to 900 °C and held for 10 h to obtain the carbon nanotube-coated single-crystalline layered oxide cathode material. The mass ratio of the usage amounts of sodium hydroxide to sodium nitrate was 1:0.194, the mass ratio of the usage amounts of sodium nitrate to ferric nitrate was 1:11.38, the mass ratio of the usage amounts of sodium nitrate to manganese nitrate was 1:5.76, the mass ratio of the usage amounts of sodium nitrate to magnesium acetate was 1:0.84, the mass ratio of the usage amounts of sodium nitrate to calcium acetate was 1:0.93, the mass ratio of the usage amounts of sodium nitrate to thiourea was 1:7.06, and the mass ratio of the usage amounts of urea to water was 1:5.81.

[0042] Example 5: Preparation of carbon nanotube-coated single-crystalline layered oxide cathode material: Sodium hydroxide, sodium nitrate, iron nitrate, manganese nitrate, magnesium acetate, calcium acetate, urea, 2-aminoethylsulfonamide, and 2-pyrazol-1-ylethylamine were added to water and stirred to obtain a mixed solution. The mixed solution was spray-dried at an inlet air temperature of 180 °C and a feed rate of 200 mL / h to obtain a dry powder precursor, and the dry powder precursor was further pulverized by air flow to obtain a pulverized dry powder precursor. The pulverized dry powder precursor was heated to 350 °C at a heating rate of 2 °C / min under nitrogen conditions and held for 6 h, and then heated to 900 °C and held for 10 h to obtain the carbon nanotube-coated single-crystalline layered oxide cathode material. The mass ratio of the usage amounts of sodium hydroxide to sodium nitrate is 1:0.194, the mass ratio of the usage amounts of sodium nitrate to iron nitrate is 1:11.38, the mass ratio of the usage amounts of sodium nitrate to manganese nitrate is 1:5.76, the mass ratio of the usage amounts of sodium nitrate to magnesium acetate is 1:0.84, the mass ratio of the usage amounts of sodium nitrate to calcium acetate is 1:0.93, the mass ratio of the usage amounts of sodium nitrate to urea is 1:9.41, the mass ratio of the usage amounts of urea to 2-aminoethylsulfonamide is 1:0.29, the mass ratio of the usage amounts of urea to 2-pyrazol-1-ylethylamine is 1:0.24, and the mass ratio of the usage amounts of urea to water is 1:5.81.

[0043] Example 6: Preparation of carbon nanotube-coated single-crystalline layered oxide cathode material: This example is different from Example 5 in that the mass ratio of the usage amounts of urea to 2-aminoethylsulfonamide is 1:0.38, and other conditions and parameters are the same as those in Example 5.

[0044] Example 7: Preparation of carbon nanotube-coated single-crystalline layered oxide cathode material: This example is different from Example 5 in that the mass ratio of the usage amounts of urea to 2-pyrazol-1-ylethylamine is 1:0.32, and other conditions and parameters are the same as those in Example 5.

[0045] Example 8: Preparation of Carbon Nanotube-Coated Single-Crystalline Layered Oxide Cathode Material: Sodium hydroxide, sodium nitrate, iron nitrate, manganese nitrate, magnesium acetate, calcium acetate, urea, 2-aminoethylsulfonamide, 2-pyrazol-1-ylethylamine, and 2-carboxyethylphenylphosphinic acid were added to water and stirred to obtain a mixed solution. The mixed solution was spray-dried at an inlet air temperature of 180 °C and a feed rate of 200 mL / h to obtain a dry powder precursor, and the dry powder precursor was further pulverized by air flow to obtain a pulverized dry powder precursor. The pulverized dry powder precursor was heated to 350 °C at a heating rate of 2 °C / min under nitrogen conditions and held for 6 h, and then heated to 900 °C and held for 10 h to obtain the carbon nanotube-coated single-crystalline layered oxide cathode material. The mass ratio of the usage amounts of sodium hydroxide to sodium nitrate is 1:0.194, the mass ratio of the usage amounts of sodium nitrate to iron nitrate is 1:11.38, the mass ratio of the usage amounts of sodium nitrate to manganese nitrate is 1:5.76, the mass ratio of the usage amounts of sodium nitrate to magnesium acetate is 1:0.84, the mass ratio of the usage amounts of sodium nitrate to calcium acetate is 1:0.93, the mass ratio of the usage amounts of sodium nitrate to urea is 1:9.41, the mass ratio of the usage amounts of sodium nitrate to 2-aminoethylsulfonamide is 1:2.75, the mass ratio of the usage amounts of sodium nitrate to 2-pyrazol-1-ylethylamine is 1:2.25, the mass ratio of the usage amounts of 2-aminoethylsulfonamide to 2-carboxyethylphenylphosphinic acid is 1:0.14, and the mass ratio of the usage amounts of urea to water is 1:5.81.

[0046] Example 9: Preparation of Carbon Nanotube-Coated Single-Crystalline Layered Oxide Cathode Material: This example is different from Example 8 in that the mass ratio of the usage amounts of 2-aminoethylsulfonamide to 2-carboxyethylphenylphosphinic acid is 1:0.25, and other conditions and parameters are the same as those in Example 8.

[0047] Comparative Example 1: Preparation of Carbon Nanotube-Coated Single-Crystalline Layered Oxide Cathode Material: This comparative example is different from Example 1 in that urea was not used, and other conditions and parameters are the same as those in Example 1.

[0048] Comparative Example 2: Preparation of Carbon Nanotube-Coated Single-Crystalline Layered Oxide Cathode Material: This comparative example is different from Example 5 in that 2-aminoethylsulfonamide was not used, and other conditions and parameters are the same as those in Example 5.

[0049] Comparative Example 3: Preparation of Carbon Nanotube-Coated Single-Crystalline Layered Oxide Cathode Material: This comparative example is different from Example 5 in that 2-pyrazol-1-ylethylamine was not used, and other conditions and parameters are the same as those in Example 5.

[0050] Experimental Example 1: The carbon nanotube-coated single-crystalline layered oxide cathode material prepared in Example 1 was observed for its electron microscopy microstructure, and the results are as Figure 1 shown.

[0051] Example 2: Preparation of button cells: The carbon nanotube-coated single-crystalline layered oxide cathode material, Super P, and polyvinylidene fluoride binder were mixed, and several zirconia beads with a diameter of 3 mm were added. The mixture was ball-milled for 4 h to obtain a mixed slurry, which was coated on aluminum foil and dried in vacuum at 100 °C for 6 h, and then cut into pieces to obtain the positive electrode sheet, which was used as the working electrode. Using metallic sodium as the counter electrode and NaClO4 electrolyte as the electrolyte, button cells were assembled under the conditions that the oxygen content in the air was ≤ 0.01% and the water content was ≤ 0.01%. The mass ratio of the high-compact sodium-ion battery composite cathode material, Super P, and polyvinylidene fluoride binder used was 96:2:2. The carbon nanotube-coated single-crystalline layered oxide cathode material included the carbon nanotube-coated single-crystalline layered oxide cathode materials prepared in Examples 1-4 and Comparative Example 1.

[0052] The button cells were subjected to constant current charge-discharge tests to obtain the reversible capacity. The test voltage window was 2.0 - 4.0 V, and the rate was 0.1 - 5C.

[0053] Table 1 Results of reversible capacity determination

[0054] As shown in Table 1, the button cells made of the carbon nanotube-coated single-crystalline layered oxide cathode material prepared in Example 1 had a relatively high reversible capacity under different rate conditions, and still had a relatively high reversible capacity at high rates of 2C and 5C, showing good rate performance.

[0055] Experimental Example 3: The preparation of button cells was the same as in Experimental Example 2. The carbon nanotube-coated single-crystalline layered oxide cathode material included the carbon nanotube-coated single-crystalline layered oxide cathode materials prepared in Examples 1-9 and Comparative Examples 1-3. The button cells were subjected to constant current charge-discharge tests to obtain the reversible capacity. The test voltage window was 2.0 - 4.0 V, and the rate was 2C.

[0056] Table 2 Results of reversible capacity determination

[0057] The measurement results of the reversible capacities of the button cells made of the carbon nanotube-coated single-crystalline layered oxide cathode materials prepared in Examples 1-9 and Comparative Examples 1-3 are shown in Table 2. Comparing Example 1 with Example 2 shows that a decrease in the amount of urea used will reduce the reversible capacity of the button cell made of the carbon nanotube-coated single-crystalline layered oxide cathode material prepared; comparing Example 1 with Examples 3-4 shows that using urea has a better effect than using melamine and thiourea, and the reversible capacity of the button cell made of the carbon nanotube-coated single-crystalline layered oxide cathode material prepared is higher; comparing Example 1 with Example 5 shows that the use of 2-aminoethylsulfonamide and 2-pyrazol-1-ylethylamine can increase the reversible capacity of the button cell made of the carbon nanotube-coated single-crystalline layered oxide cathode material prepared; comparing Example 5 with Examples 6-7 shows that an increase in the amount of 2-aminoethylsulfonamide and 2-pyrazol-1-ylethylamine used within a certain range can also increase the reversible capacity of the button cell made of the carbon nanotube-coated single-crystalline layered oxide cathode material prepared; comparing Example 5 with Example 8 shows that on the basis of using 2-aminoethylsulfonamide and 2-pyrazol-1-ylethylamine, using 2-carboxyethylphenylphosphinic acid can further increase the reversible capacity of the button cell made of the carbon nanotube-coated single-crystalline layered oxide cathode material prepared; comparing Example 1 with Comparative Example 1 shows that the preparation of the carbon nanotube-coated single-crystalline layered oxide cathode material requires an appropriate amount of urea to be used, otherwise the reversible capacity of the button cell made will decrease; comparing Example 5 with Comparative Examples 1-2 shows that 2-aminoethylsulfonamide and 2-pyrazol-1-ylethylamine need to be used together, and using any one of 2-aminoethylsulfonamide and 2-pyrazol-1-ylethylamine alone has no obvious effect on improving the reversible capacity of the button cell made of the carbon nanotube-coated single-crystalline layered oxide cathode material prepared.

[0058] Experimental Example 4: The button cells were prepared in the same way as in Experimental Example 2. The carbon nanotube-coated single-crystalline layered oxide cathode materials include the carbon nanotube-coated single-crystalline layered oxide cathode materials prepared in Examples 1-9 and Comparative Examples 1-3. The cycle life of the button cells was tested to obtain the capacity retention rate after 100 cycles. The test voltage window was 2.0 - 4.0 V and the rate was 2C.

[0059] Table 3 Measurement results of capacity retention rate

[0060] The measurement results of the capacity retention rate are shown in Table 3. The measurement results of the capacity retention rate of the button cells made of the carbon nanotube-coated single-crystalline layered oxide cathode materials prepared in Examples 1-9 and Comparative Examples 1-3 are shown in Table 3. Comparing Example 1 with Example 2 shows that a decrease in the amount of urea used will reduce the capacity retention rate of the button cells made of the carbon nanotube-coated single-crystalline layered oxide cathode materials prepared; comparing Example 1 with Examples 3-4 shows that using urea has a better effect than using melamine and thiourea, and the capacity retention rate of the button cells made of the carbon nanotube-coated single-crystalline layered oxide cathode materials prepared is higher; comparing Example 1 with Example 5 shows that the use of 2-aminoethylsulfonamide and 2-pyrazol-1-ylethylamine can increase the capacity retention rate of the button cells made of the carbon nanotube-coated single-crystalline layered oxide cathode materials prepared; comparing Example 5 with Examples 6-7 shows that an increase in the amount of 2-aminoethylsulfonamide and 2-pyrazol-1-ylethylamine used within a certain range can also increase the capacity retention rate of the button cells made of the carbon nanotube-coated single-crystalline layered oxide cathode materials prepared; comparing Example 5 with Example 8 shows that on the basis of using 2-aminoethylsulfonamide and 2-pyrazol-1-ylethylamine, using 2-carboxyethylphenylphosphinic acid can further increase the reversible capacity of the button cells made of the carbon nanotube-coated single-crystalline layered oxide cathode materials prepared; comparing Example 1 with Comparative Example 1 shows that the preparation of the carbon nanotube-coated single-crystalline layered oxide cathode materials requires an appropriate amount of urea, otherwise the reversible capacity of the button cells made will decrease; comparing Example 5 with Comparative Examples 1-2 shows that 2-aminoethylsulfonamide and 2-pyrazol-1-ylethylamine need to be used together. Using any one of 2-aminoethylsulfonamide and 2-pyrazol-1-ylethylamine alone has no obvious effect on improving the reversible capacity of the button cells made of the carbon nanotube-coated single-crystalline layered oxide cathode materials prepared.

[0061] The above-described embodiments and / or implementation manners are only used to illustrate the preferred embodiments and / or implementation manners for realizing the technology of the present invention, and do not impose any formal restrictions on the implementation manners of the technology of the present invention. Any person skilled in the art, without departing from the scope of the technical means disclosed in the content of the present invention, may make some changes or modifications to other equivalent embodiments, but should still be regarded as the same technology or embodiment as the present invention in essence.

[0062] In this article, specific examples are used to elaborate on the principles and implementation manners of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application. The above description is only the preferred implementation manner of the present application. It should be noted that due to the limited nature of literal expression and objectively infinite specific structures, for those of ordinary skill in the art, without departing from the principles of the present application, several improvements, refinements or changes can be made, or the above technical features can be combined in an appropriate manner; these improvements, refinements, changes or combinations, or directly applying the inventive concept and technical solution to other occasions without improvement, shall all be regarded as the protection scope of the present application.

Claims

1. A preparation method of a carbon nanotube-coated single-crystal layered oxide cathode material, comprising: Adding an alkali, a sodium salt, an iron salt, a manganese salt, a magnesium salt, a calcium salt, and an amino compound into a solvent and stirring to obtain a mixed solution. The mixed solution is subjected to spray drying and airflow pulverization to obtain a pulverized dry powder precursor, and the pulverized dry powder precursor is subjected to high-temperature carbonization under nitrogen conditions to obtain the carbon nanotube-coated single-crystal layered oxide cathode material; the mass ratio of the usage amount of the sodium salt to the amino compound is 1:2 - 16.

2. The preparation method of a carbon nanotube-coated single-crystalline layered oxide cathode material according to claim 1, characterized in that: The alkali is sodium hydroxide, and the sodium salt is at least one of sodium carbonate, sodium bicarbonate, sodium sulfate, sodium nitrate, sodium chloride, and sodium oxalate. The mass ratio of the usage amount of the alkali to the sodium salt is 1:0.1 - 0.

3.

3. The preparation method of a carbon nanotube-coated single-crystalline layered oxide cathode material according to claim 1, wherein: The iron salt is at least one of ferrous oxalate, iron nitrate, ferrous acetate, ferrous sulfate, ferrous acetate, and ferrous chloride. The mass ratio of the usage amount of the sodium salt to the iron salt is 1:10 - 13.

4. The preparation method of a carbon nanotube-coated single crystal layered oxide cathode material according to claim 1, characterized in that: The manganese salt is at least one of manganese nitrate, manganese chloride, manganese oxalate, manganese acetate, manganese sulfate, and manganese acetylacetonate. The mass ratio of the usage amount of the sodium salt to the manganese salt is 1:5 - 7.

5. The preparation method of a carbon nanotube-coated single-crystalline layered oxide cathode material according to claim 1, wherein: The magnesium salt is at least one of magnesium nitrate, magnesium acetate, magnesium chloride, magnesium sulfate, and magnesium oxalate. The mass ratio of the usage amount of the sodium salt to the magnesium salt is 1:0.5 - 1.

2.

6. The preparation method of a carbon nanotube-coated single-crystal layered oxide cathode material according to claim 1, wherein: The calcium salt is at least one of calcium nitrate, calcium sulfate, calcium chloride, calcium oxalate, and calcium acetate. The mass ratio of the usage amount of the sodium salt to the calcium salt is 1:0.6 - 1.

2.

7. The preparation method of a carbon nanotube-coated single-crystalline layered oxide cathode material according to claim 1, characterized in that: The amino compound is at least one of urea, thiourea, melamine, 2-aminoethylsulfonamide, 2-pyrazol-1-ylethylamine, triethylenediamine, cyclohexeneimine, and isopropanolamine. The mass ratio of the usage amount of urea to 2-aminoethylsulfonamide is 1:0.2 - 0.4, and the mass ratio of the usage amount of urea to 2-pyrazol-1-ylethylamine is 1:0.2 - 0.

4.

8. The preparation method of a carbon nanotube-coated single crystal layered oxide cathode material according to claim 1, characterized in that: The solvent is water, and the mass ratio of the usage amount of the amino compound to the solvent is 1:5 - 8.

9. The preparation method of a carbon nanotube-coated single-crystalline layered oxide cathode material according to claim 1, characterized in that: The inlet air temperature of the spray drying is 160 - 200 °C, the feeding rate is 190 - 210 mL / h, the heating rate of the high-temperature carbonization is 1.5 - 3 °C / min. First, it is heated to 300 - 400 °C and kept warm for 5 - 7 h, and then heated to 800 - 1000 °C and kept warm for 9 - 12 h.

10. Application of the carbon nanotube-coated single-crystal layered oxide cathode material prepared by the preparation method according to any one of claims 1 - 9 in the preparation of a battery.

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