Long-life high-nickel ternary positive electrode material and preparation method thereof

Abstract

The application discloses a long-life high-nickel ternary positive electrode material and a preparation method thereof. The high-nickel ternary positive electrode material contains sulfur ions in a superficial layer. The high-nickel ternary positive electrode material with a surface layer oxygen-deficient structure has sulfur ions introduced into the surface, can reconstruct the superficial layer of the high-nickel ternary positive electrode material, and achieves the goal of improving the service cycle life of the high-nickel ternary positive electrode material.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lithium batteries, in particular, the present application relates to a long-life high-nickel ternary cathode material and a preparation method thereof. BACKGROUND

[0002] With the rapid growth of electric vehicles in recent years, the problem of range anxiety is increasingly prominent, and the demand for higher energy density materials by lithium batteries is increasing. High-nickel ternary cathode materials, due to their high reversible energy density, to some extent, meet the demand of long-range, and are gradually applied in new energy electric vehicles on a large scale. However, high-nickel ternary cathode materials, due to the high content of nickel, lead to the decline of the stability of the material, the significant increase of the surface residual alkali, the increase of the interface side reaction between the electrolyte, the enhancement of the water absorption, etc., and thus the service life of high-nickel ternary cathode materials is seriously affected.

[0003] In view of the short service life of high-nickel ternary cathode materials, the industry usually adopts methods such as doping, multi-element doping, water washing and surface modification to inhibit or improve. For example: patent CN113764647A discloses a ternary cathode material doped with Zr and multi-anions, a preparation method thereof and a lithium ion battery, uses zirconium and multiple combinations of fluorine, chlorine and sulfur, uses coprecipitation method to prepare corresponding ternary precursor, and then uses high-temperature solid phase method to prepare corresponding ternary cathode material. Since the atmosphere used in the preparation process of the ternary cathode material is oxidizing, the S 2- as a multi-anion source has a theoretical error; patent CN114162881A discloses a fluorine-doped ternary cathode material, adopts a coprecipitation method to precipitate fluorine into the precursor during the preparation of the precursor, then mixes the precursor with a lithium source, and finally obtains a fluorine-doped ternary cathode material by high-temperature solid phase method. Although fluorine doping can inhibit the oxygen precipitation of the ternary cathode material to some extent, fluorine has a strong corrosion on the equipment, and the patent adopts a coprecipitation method, so the distribution of fluorine is uniform, which improves the problem of oxygen precipitation of the ternary cathode material, but leads to a serious deterioration of the energy density of the material. SUMMARY

[0004] Based on the oxygen release of lithium ion high nickel ternary positive electrode material in the prior art, the side reaction with electrolyte is serious, which causes the defects of poor life and poor cycle performance of the high nickel ternary positive electrode material, the present application provides a long cycle high nickel ternary positive electrode material and a preparation method thereof, according to the method of the embodiment of the present application, first, the surface of the high nickel ternary positive electrode material is heat treated by using a carbon source, so that the surface of the high nickel ternary positive electrode material forms an oxygen-deficient phase, then the sulfur source is mixed with the high nickel ternary positive electrode material with the oxygen-deficient structure on the surface in a certain proportion, and the purpose of introducing sulfur ions into the surface of the high nickel ternary positive electrode material with the surface oxygen-deficient structure is achieved by grinding or heating, and then the surface layer of the high nickel ternary positive electrode material is reconstructed, so as to improve the cycle life of the high nickel ternary positive electrode material.

[0005] In the first aspect of the present application, the present application provides a high nickel ternary positive electrode material. According to the embodiment of the present application, the surface layer of the high nickel ternary positive electrode material contains sulfur ions. The inventors found that introducing sulfur ions into the surface of the high nickel ternary positive electrode material with the surface oxygen-deficient structure can reconstruct the surface layer of the high nickel ternary positive electrode material, so as to improve the cycle life of the high nickel ternary positive electrode material.

[0006] In another aspect of the present application, the present application also provides a method for preparing a high nickel ternary positive electrode material. According to the embodiment of the present application, the method comprises:

[0007] 1) the high nickel ternary positive electrode material to be improved, the carbon source is subjected to first mixing treatment and first heating treatment to obtain intermediate A;

[0008] 2) the intermediate A is subjected to second mixing treatment, grinding treatment or second heating treatment with a sulfur source to obtain the high nickel ternary positive electrode material. According to the method of the embodiment of the present application, first, the surface of the high nickel ternary positive electrode material is heat treated by using a carbon source, so that the surface of the high nickel ternary positive electrode material forms an oxygen-deficient phase, then the sulfur source is mixed with the high nickel ternary positive electrode material with the oxygen-deficient structure on the surface in a certain proportion, and the purpose of introducing sulfur ions into the surface of the high nickel ternary positive electrode material with the surface oxygen-deficient structure is achieved by grinding or heating, and then the surface layer of the high nickel ternary positive electrode material is reconstructed, so as to improve the cycle life of the high nickel ternary positive electrode material.

[0009] According to the embodiment of the present application, the above method can further comprise at least one of the following accessory technical features:

[0010] According to the embodiment of the present application, the carbon source comprises one or more selected from glucose, sucrose, fructose, nanocellulose, amorphous carbon powder, starch, PEG1000 and PEG2000.

[0011] According to the embodiment of the present application, the carbon source is glucose.

[0012] According to an embodiment of the present application, the mass ratio of the high-nickel ternary cathode material to be improved to the carbon source is 0.1% to 0.5%, wherein the mass measurement of the carbon source is in the form of the theoretical residual carbon content of the carbon source.

[0013] According to an embodiment of the present application, the sulfur source includes one or more selected from hydrogen sulfide, carbon disulfide, molybdenum disulfide, lithium sulfide, diphosphorus pentasulfide, and ammonium sulfide.

[0014] According to an embodiment of the present application, the mass ratio of the sulfur source to the high-nickel ternary cathode material to be improved is 2000 ppm, wherein the sulfur source is measured in terms of sulfur element.

[0015] According to an embodiment of the present application, the molar content of nickel in the high-nickel ternary cathode material to be improved accounts for Ni / (Ni+Co+Mn)≥0.8.

[0016] According to an embodiment of the present application, the first mixing treatment is performed in a mixer.

[0017] According to an embodiment of the present application, the first heating treatment is performed in an inert atmosphere.

[0018] According to an embodiment of the present application, the temperature of the first heating treatment is 400 to 600°C.

[0019] According to an embodiment of the present application, the time of the first heating treatment is 5 to 8 hours.

[0020] According to an embodiment of the present application, the grinding treatment is performed in an inert atmosphere.

[0021] According to an embodiment of the present application, the second heating treatment is performed in an inert atmosphere.

[0022] According to an embodiment of the present application, the temperature of the second heating treatment is 100 to 150°C.

[0023] According to an embodiment of the present application, the time of the second heating treatment is 6 to 10 hours.

[0024] According to an embodiment of the present application, the second heating treatment further includes cooling the material obtained by the second heating treatment to room temperature and performing a crushing and screening treatment.

[0025] In still another aspect of the present application, the present application further provides a high-nickel ternary cathode material. According to an embodiment of the present application, the high-nickel ternary cathode material is prepared according to the method described above.

[0026] In still another aspect of the present application, the present application further provides a battery. According to an embodiment of the present application, the battery comprises the high-nickel ternary positive electrode material as described above or the high-nickel ternary positive electrode material prepared according to the method as described above.

[0027] According to an embodiment of the present application, the sulfur ion belongs to Lewis base, can absorb hydrogen fluoride generated in the electrolyte to a certain extent, thereby inhibiting the corrosion of hydrogen fluoride to the surface of the high-nickel ternary positive electrode material, so as to achieve the effect of improving the cycle life of the ternary positive electrode material; at the same time, the sulfur ion replaces part of the oxygen ions in the superficial layer of the high-nickel ternary positive electrode material particles, so that the superficial layer of the ternary positive electrode material is restructured, which can well inhibit the oxygen release from the surface of the high-nickel ternary positive electrode material and the structure collapse caused by the oxygen release, thereby improving the gas production problem and the cycle life problem of the high-nickel positive electrode material. BRIEF DESCRIPTION OF DRAWINGS

[0028] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the following description, taken in conjunction with the following drawings, in which:

[0029] Figure 1 is the cycle discharge capacity of the button cell according to the embodiment of the present application. DETAILED DESCRIPTION

[0030] The embodiments described below are exemplary and are intended to be illustrative of the present application, and are not to be construed as limiting the present application.

[0031] Furthermore, the terms "first", "second", "third", etc. are used herein for descriptive purposes only and are not to be construed as indicating or implying relative importance or a significant relationship between the indicated technical features. Thus, a feature defined with "first", "second" or "third" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise explicitly and specifically limited.

[0032] The present application is described below with reference to specific embodiments, it should be noted that these embodiments are merely descriptive and do not limit the present application in any way.

[0033] Example 1

[0034] First, a certain amount of high-nickel ternary positive electrode material (the molar content of nickel accounts for Ni / (Ni+Co+Mn)≥0.8) and glucose are weighed respectively. The mass ratio of the high-nickel ternary positive electrode material to the carbon source is 0.3%, and the mass measurement of the carbon source is the theoretical residual carbon content of the carbon source.

[0035] Then, the weighed high-nickel ternary positive electrode material and carbon source are poured into a mixer and mixed uniformly.

[0036] Then the mixed material is heat treated at 500°C for 6h in inert atmosphere to obtain intermediate A.

[0037] Then a certain amount of intermediate A and sulfiding ammonia are weighed respectively, and the mass ratio of the sulfur source to the positive electrode material is 2000ppm, wherein the sulfur source is measured by sulfur element.

[0038] Then the mixed material is ground or heat treated at 130°C for 8h in inert atmosphere, and finally the heat treated material is cooled to room temperature, and then crushed, sieved and treated in a temperature controlled environment to obtain anion modified high nickel ternary positive electrode material.

[0039] Example 2

[0040] First, a certain amount of high nickel ternary positive electrode material (molar content of nickel is Ni / (Ni+Co+Mn)≥0.8) and glucose are weighed respectively. The mass ratio of high nickel ternary positive electrode material to carbon source is 0.1%, and the mass measurement of carbon source is the theoretical residual carbon content of carbon source.

[0041] Then the weighed high nickel ternary positive electrode material and carbon source are poured into a mixer and mixed evenly.

[0042] Then the mixed material is heat treated at 600°C for 5h in inert atmosphere to obtain intermediate A.

[0043] Then a certain amount of intermediate A and one or more of sulfiding ammonia are weighed respectively, and the mass ratio of the sulfur source to the positive electrode material is 3000ppm, wherein the sulfur source is measured by sulfur element.

[0044] Then the mixed material is ground or heat treated at 100°C for 10h in inert atmosphere, and finally the heat treated material is cooled to room temperature, and then crushed, sieved and treated in a temperature controlled environment to obtain anion modified high nickel ternary positive electrode material.

[0045] Example 3

[0046] First, a certain amount of high nickel ternary positive electrode material (molar content of nickel is Ni / (Ni+Co+Mn)≥0.8) and glucose are weighed respectively. The mass ratio of high nickel ternary positive electrode material to carbon source is 0.5%, and the mass measurement of carbon source is the theoretical residual carbon content of carbon source.

[0047] Then the weighed high nickel ternary positive electrode material and carbon source are poured into a mixer and mixed evenly.

[0048] Then the mixed material is heat treated at 400°C for 8h in inert atmosphere to obtain intermediate A.

[0049] Then a certain amount of intermediate A and sulfiding ammonia are weighed, and the mass ratio of the sulfide source to the positive electrode material is 1000 ppm, wherein the sulfide source is measured by sulfur element, and then the two materials are uniformly mixed.

[0050] Then the mixture is ground or heat treated at 150°C for 6h in an inert atmosphere, and finally the heat treated material is cooled to room temperature and processed by crushing and sieving in a temperature controlled environment to obtain anion modified high nickel ternary positive electrode material.

[0051] Comparative Example 1

[0052] A certain amount of high nickel ternary positive electrode material (molar content of nickel is Ni / (Ni+Co+Mn)≥0.8) is weighed, and then the high nickel ternary positive electrode material is heat treated at 130°C for 8h in an inert atmosphere, and finally the heat treated material is cooled to room temperature and processed by crushing and sieving in a temperature controlled environment.

[0053] Comparative Example 2

[0054] A certain amount of high nickel ternary positive electrode material (molar content of nickel is Ni / (Ni+Co+Mn)≥0.8) is weighed, and then the high nickel ternary positive electrode material is heat treated at 130°C for 8h in an inert atmosphere, and finally the heat treated material is cooled to room temperature and processed by crushing and sieving in a temperature controlled environment.

[0055] Button cell preparation: The positive electrode materials prepared in Examples 1-2 and Comparative Examples 1-2 are assembled into button cells as follows: The positive electrode material, conductive agent (acetylene black) and binder (PVDF) are weighed according to a mass ratio of 90%:5%:5%, and the weighed positive electrode material and acetylene black are mixed and ground in a marquis mortar. After uniform grinding, they are added to N-methyl pyrrolidone (NMP) which has been fully reacted with PVDF and continuously ground until the slurry becomes a viscous liquid with certain fluidity. The ground slurry is uniformly transferred to an aluminum foil, and the sample is uniformly coated using a coater with a thickness of 300μm. Subsequently, it is pre-baked at 60°C in air for 5 hours, then vacuumized, and dried at 90°C for 12 hours to remove water and organic matter in the coated sample. The electrode sheet is cut to size for standby use, and a positive electrode sheet is obtained.

[0056] Lithium sheet is used as the negative electrode, the prepared electrode sheet is used as the positive electrode, the electrolyte ratio is EC:DMC=1:1, and a button cell is assembled. The charge and discharge test is performed using a BTV charge and discharge tester. Under the condition of 25°C, the lithium ion battery assembled with the above positive electrode sheet is subjected to 0.5C / 1C charge and discharge cycles under a working voltage of 3.0-4.3V. The cycle discharge capacity curve of the button cell is shown in Figure 1 From Figure 1 It can be seen that the cycle improvement of Examples 1 and 2 is very obvious compared with Comparative Example 1, and the cycle improvement of the dry coating method of Comparative Example 2 is also obvious.

[0057] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Also, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. Furthermore, the person skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples, without contradiction.

[0058] Although the embodiments of the present application have been shown and described above, it is understood that the above-described embodiments are exemplary and are not to be construed as limiting the present application, and the person skilled in the art can make changes, modifications, replacements and variations to the above-described embodiments within the scope of the present application.

Claims

1. A method for preparing high-nickel ternary cathode materials, characterized in that, include: 1) The high-nickel ternary cathode material to be improved and the carbon source are subjected to a first mixing treatment and a first heating treatment to obtain intermediate A. The mass ratio of the high-nickel ternary cathode material to be improved to the carbon source is 0.1%~0.5%, wherein the mass measurement method of the carbon source is the theoretical residual carbon content of the carbon source. The first heating treatment is carried out in an inert atmosphere, the temperature of the first heating treatment is 400~600℃, and the time of the first heating treatment is 5~8h. 2) The intermediate A is mixed with a sulfur source in a second mixing process, followed by grinding or a second heating process to obtain the high-nickel ternary cathode material. The second heating process is carried out in an inert atmosphere, the temperature of the second heating process is 100~150℃, and the time of the second heating process is 6~10h. The grinding process is carried out in an inert atmosphere. The carbon source includes one or more selected from glucose, sucrose, fructose, nanocellulose, amorphous carbon powder, starch, PEG1000, and PEG2000; The sulfur source includes one or more selected from hydrogen sulfide, carbon disulfide, molybdenum disulfide, lithium sulfide, phosphorus pentasulfide, and ammonia sulfide; The mass ratio of the sulfur source to the high-nickel ternary cathode material to be improved is 2000 ppm, wherein the sulfur source is measured in terms of elemental sulfur.

2. The method according to claim 1, characterized in that, The carbon source is glucose.

3. The method according to claim 1, characterized in that, The nickel molar content ratio in the high-nickel ternary cathode material to be improved is Ni / (Ni+Co+Mn)≥0.

8.

4. The method according to claim 1, characterized in that, The first mixing process is carried out in a mixer.

5. The method according to claim 1, characterized in that, The second heat treatment further includes cooling the material obtained from the second heat treatment to room temperature and then crushing and sieving it.

6. A high-nickel ternary cathode material, characterized in that, The high-nickel ternary cathode material is prepared by the method according to any one of claims 1-5.

7. A battery, characterized in that, The battery comprises the high-nickel ternary cathode material of claim 6 or the high-nickel ternary cathode material prepared by the method according to any one of claims 1-5.

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