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

Abstract

The invention discloses a long-life high-nickel ternary positive electrode material and a preparation method thereof. The shallow surface layer of the high-nickel ternary positive electrode material contains sulfur ions. Sulfur ions are introduced into the surface of the high-nickel ternary positive electrode material with the surface layer oxygen-deficient structure, so that the shallow surface layer of the high-nickel ternary positive electrode material can be reconstructed, and the purpose of prolonging the service cycle life of the high-nickel ternary positive electrode material is achieved.

Description

Technical Field

[0001] The present invention relates to the field of lithium batteries, and in particular to a long-life high-nickel ternary positive electrode material and a preparation method thereof. Background Art

[0002] With the rapid growth of electric vehicles in recent years, along with the increasingly prominent problem of battery life anxiety, the demand for lithium batteries for materials with higher energy density is increasing. High-nickel ternary positive electrode materials have a high reversible energy density, which to a certain extent meets people's needs for long battery life and has gradually been widely used in new energy electric vehicles. However, due to the high nickel content, high-nickel ternary positive electrode materials have reduced material stability, significantly increased surface residual alkali, increased interfacial side reactions with the electrolyte, enhanced water absorption, etc., which in turn seriously affects the service life of high-nickel ternary positive electrode materials.

[0003] In order to solve the problem of short cycle life of high-nickel ternary positive electrode materials, the industry usually adopts doping, multi-element doping, water washing and surface modification methods to suppress or improve it. For example: Patent CN113764647A discloses a ternary positive electrode material co-doped with Zr and multiple anions, its preparation method and lithium-ion battery, using various combinations of zirconium and fluorine, chlorine and sulfur, and using a co-precipitation method to prepare the corresponding ternary precursor, and then using a high-temperature solid phase method to prepare the corresponding ternary positive electrode material. Since the atmosphere used in the preparation of the ternary positive electrode material is oxidizing, the S claimed in the patent is 2- As a kind of polyanion source, it has theoretical errors; Patent CN114162881A discloses a fluorine-doped ternary cathode material, which uses a coprecipitation method to precipitate fluorine into the precursor during the precursor preparation process, and then uses the precursor to mix with a lithium source, and finally obtains a fluorine-doped ternary cathode material by a high-temperature solid phase method. Although fluorine doping can inhibit the oxygen precipitation of ternary cathode materials to a certain extent, fluorine has a high corrosion intensity on equipment, and the patent adopts a coprecipitation method, and the distribution of fluorine is relatively uniform. While improving the oxygen precipitation problem of ternary cathode materials, it leads to a serious deterioration in the energy density of the material. Summary of the invention

[0004] Based on the defects of the prior art that lithium ion high-nickel ternary positive electrode materials release oxygen and have serious side reactions with the electrolyte, resulting in poor life and cycle performance of the high-nickel ternary positive electrode materials, the present invention provides a long-cycle high-nickel ternary positive electrode material and a preparation method thereof. According to the method of an embodiment of the present invention, a carbon source is first used to heat treat the surface of the high-nickel ternary positive electrode material to form an oxygen-deficient phase on the surface of the high-nickel ternary positive electrode material, and then a sulfur source is mixed with the obtained high-nickel ternary positive electrode material with an oxygen-deficient structure on the surface in a certain proportion, and the mixture is ground or heated to achieve the purpose of introducing sulfur ions on the surface of the high-nickel ternary positive electrode material with a surface oxygen-deficient structure, thereby reconstructing the shallow surface layer of the high-nickel ternary positive electrode material to achieve the goal of improving the cycle life of the high-nickel ternary positive electrode material.

[0005] In the first aspect of the present invention, the present invention proposes a high-nickel ternary positive electrode material. According to an embodiment of the present invention, the shallow surface layer of the high-nickel ternary positive electrode material contains sulfur ions. The inventors have found that the introduction of sulfur ions on the surface of the high-nickel ternary positive electrode material with a surface oxygen-deficient structure can reconstruct the shallow surface layer of the high-nickel ternary positive electrode material, thereby achieving the goal of improving the cycle life of the high-nickel ternary positive electrode material.

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

[0007] 1) subjecting the high-nickel ternary positive electrode material to be improved and the carbon source to a first mixing treatment and a first heating treatment to obtain an intermediate A;

[0008] 2) The intermediate A is subjected to a second mixing treatment, grinding treatment or a second heating treatment with a sulfur source to obtain the high-nickel ternary positive electrode material. The method according to an embodiment of the present invention first uses a carbon source to heat treat the surface of the high-nickel ternary positive electrode material to form an oxygen-deficient phase on the surface of the high-nickel ternary positive electrode material, and then the sulfur source is mixed with the obtained high-nickel ternary positive electrode material having an oxygen-deficient structure on the surface in a certain proportion, and the purpose of introducing sulfur ions on the surface of the high-nickel ternary positive electrode material having an oxygen-deficient structure on the surface is achieved by grinding or heating, thereby reconstructing the shallow surface layer of the high-nickel ternary positive electrode material to achieve the goal of improving the cycle life of the high-nickel ternary positive electrode material.

[0009] According to an embodiment of the present invention, the above method may further include at least one of the following additional technical features:

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

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

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

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

[0014] According to an embodiment of the present invention, the mass ratio of the sulfur source to the high-nickel ternary positive electrode 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 invention, the molar content of nickel in the high-nickel ternary positive electrode material to be improved is Ni / (Ni+Co+Mn)≥0.8.

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

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

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

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

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

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

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

[0023] According to an embodiment of the present invention, the second heating treatment is performed for 6 to 10 hours.

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

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

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

[0027] According to an embodiment of the present invention, sulfur ions are Lewis bases and can absorb hydrogen fluoride produced in the electrolyte to a certain extent, thereby inhibiting the corrosion of hydrogen fluoride on the surface of the high-nickel ternary positive electrode material, thereby achieving the effect of improving the cycle life of the ternary positive electrode material; at the same time, sulfur ions replace part of the oxygen ions in the shallow surface layer of the high-nickel ternary positive electrode material particles, so that the shallow surface layer of the ternary positive electrode material is reconstructed, which can effectively inhibit the release of oxygen on the surface of the high-nickel ternary positive electrode material and the structural collapse caused by the oxygen release, thereby improving the gas production problem and cycle life problem of the high-nickel positive electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0029] Figure 1 It is the cycle discharge capacity of the button battery according to the embodiment of the invention. DETAILED DESCRIPTION

[0030] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0031] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

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

[0033] Example 1

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

[0035] Then pour the weighed high-nickel ternary positive electrode material and carbon source into a mixer and mix them thoroughly.

[0036] The mixture was then heat treated at 500°C for 6 h in an inert atmosphere to obtain intermediate A.

[0037] Then, a certain amount of intermediate A and ammonium sulfide are weighed respectively, and the mass ratio of the sulfur source to the positive electrode material is 2000ppm, wherein the sulfur source is measured as sulfur element, and then the two materials are mixed evenly.

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

[0039] Example 2

[0040] First, a certain amount of high-nickel ternary positive electrode material (nickel molar content ratio 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%, wherein the mass measurement method of carbon source is the theoretical residual carbon content of carbon source.

[0041] Then pour the weighed high-nickel ternary positive electrode material and carbon source into a mixer and mix them thoroughly.

[0042] The mixture was then heat treated at 600°C for 5 h in an inert atmosphere to obtain intermediate A.

[0043] Then, a certain amount of intermediate A and one or more of ammonium sulfide are weighed respectively, the mass ratio of the sulfur source to the positive electrode material is 3000 ppm, wherein the sulfur source is measured as sulfur element, and then the two materials are mixed evenly.

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

[0045] Example 3

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

[0047] Then pour the weighed high-nickel ternary positive electrode material and carbon source into a mixer and mix them thoroughly.

[0048] The mixture was then heat treated at 400°C for 8 h in an inert atmosphere to obtain intermediate A.

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

[0050] The mixed material is then ground in an inert atmosphere or heat treated at 150°C for 6 hours. Finally, the heat-treated material is cooled to room temperature and crushed and screened in a temperature-controlled environment to obtain an anion-modified high-nickel ternary positive electrode material.

[0051] Comparative Example 1

[0052] A certain amount of high-nickel ternary positive electrode material (nickel molar content ratio is Ni / (Ni+Co+Mn)≥0.8) was weighed, and then the high-nickel ternary positive electrode material was heat treated at 130°C in an inert atmosphere for 8 hours. Finally, the heat-treated material was cooled to room temperature and crushed and screened in a temperature-controlled environment.

[0053] Comparative Example 2

[0054] A certain amount of high-nickel ternary positive electrode material (nickel molar content ratio is Ni / (Ni+Co+Mn)≥0.8) is weighed and crushed and screened in a temperature-controlled environment.

[0055] Preparation of button cells: Preparation of button cells: The positive electrode materials prepared in the above Examples 1 to 2 and Comparative Examples 1 to 2 are respectively assembled as follows: The positive electrode material, the conductive agent (acetylene black) and the binder (PVDF) are weighed in a mass ratio of 90%:5%:5%, and the weighed positive electrode material and acetylene black are mixed and ground in an agate mortar. After grinding evenly, they are added to N-methylpyrrolidone (NMP) that has been fully reacted with PVDF and continuously ground until the slurry becomes a viscous liquid with a certain fluidity. The ground slurry is evenly transferred to aluminum foil, and the sample is evenly coated with a coater with a thickness of 300 μm, followed by pre-baking in air at 60°C for 5 hours, and then vacuuming and drying at 90°C for 12 hours to achieve the purpose of removing water and organic matter in the coated sample, and the electrode sheet is cut out according to size for use to obtain the positive electrode sheet.

[0056] The lithium sheet was used as the negative electrode, the prepared electrode sheet was used as the positive electrode, the electrolyte ratio was EC:DMC=1:1, and button cells were assembled. The charge and discharge test was performed using a BTV charge and discharge tester. At 25°C, the lithium-ion battery assembled with the above positive electrode sheet was charged and discharged at 0.5C / 1C at a working voltage of 3.0-4.3V. The button battery cycle discharge capacity curve is shown in Figure 1 ,from Figure 1 It can be seen that the cycle of Example 1 and Example 2 is significantly improved compared with Comparative Example 1, and the dry coating cycle is also significantly improved compared with Comparative Example 2.

[0057] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0058] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A high nickel ternary cathode material, It is characterized in that The shallow surface layer of the high-nickel ternary positive electrode material contains sulfur ions.

2. A method for preparing a high-nickel ternary positive electrode material, It is characterized in that include: 1) subjecting the high-nickel ternary positive electrode material to be improved and the carbon source to a first mixing treatment and a first heating treatment to obtain an intermediate A; 2) subjecting the intermediate A and a sulfur source to a second mixing treatment, a grinding treatment or a second heating treatment to obtain the high-nickel ternary positive electrode material.

3. The method according to claim 2, It is characterized in that The carbon source includes one or more selected from glucose, sucrose, fructose, nanocellulose, amorphous carbon powder, starch, PEG1000, and PEG2000; Preferably, the carbon source is glucose; Optionally, the mass ratio of the high-nickel ternary positive electrode material to be improved to the carbon source is 0.1% to 0.5%, wherein the mass measurement method of the carbon source is the theoretical residual carbon content of the carbon source.

4. The method according to claim 2, It is characterized in that The sulfur source includes one or more selected from hydrogen sulfide, carbon disulfide, molybdenum disulfide, lithium sulfide, phosphorus pentasulfide, and ammonium sulfide; Optionally, the mass ratio of the sulfur source to the high-nickel ternary positive electrode material to be improved is 2000 ppm, wherein the sulfur source is measured in terms of sulfur element.

5. The method according to claim 2, It is characterized in that The molar content of nickel in the high-nickel ternary positive electrode material to be improved is Ni / (Ni+Co+Mn)≥0.

8.

6. The method according to claim 2, It is characterized in that The first mixing process is carried out in a mixer; Optionally, the first heating treatment is performed in an inert atmosphere; Optionally, the temperature of the first heating treatment is 400-600°C; Optionally, the first heating treatment is performed for 5 to 8 hours.

7. The method according to claim 2, It is characterized in that The grinding process is carried out in an inert atmosphere; Optionally, the second heat treatment is performed in an inert atmosphere; Optionally, the temperature of the second heating treatment is 100-150°C; Optionally, the second heating treatment is performed for 6 to 10 hours.

8. The method according to claim 2, It is characterized in that The second heating treatment further includes cooling the material obtained from the second heating treatment to room temperature and performing crushing and screening treatments.

9. A high nickel ternary cathode material, It is characterized in that The high-nickel ternary positive electrode material is prepared according to the method described in any one of claims 2-8.

10. A battery, It is characterized in that The battery comprises the high-nickel ternary positive electrode material according to claim 1 or 9 or the high-nickel ternary positive electrode material prepared by the method according to any one of claims 2-8.

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