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

Abstract

This invention discloses a long-cycle high-nickel ternary cathode material and its preparation method, wherein the oxygen in the shallow surface layer of the high-nickel ternary cathode material is replaced by anionic sulfur. This high-nickel ternary cathode material exhibits long lifespan and good cycle performance.

Description

Technical Field

[0001] This invention relates to the field of lithium batteries, specifically to a long-cycle high-nickel ternary cathode material and its preparation method. Background Technology

[0002] With the rapid growth of electric vehicles in recent years, and the increasing prominence of range anxiety, the demand for higher energy density materials in lithium batteries is soaring. High-nickel ternary cathode materials, due to their high reversible energy density, have met the demand for longer driving ranges to some extent and are gradually being widely used in new energy electric vehicles. However, the high nickel content of high-nickel ternary cathode materials leads to decreased material stability, significantly increased surface residual alkali, increased interfacial side reactions with the electrolyte, and enhanced water absorption, thus severely impacting the lifespan of high-nickel ternary cathode materials.

[0003] To address the short cycle life of high-nickel ternary cathode materials, the industry typically employs doping, multi-element doping, water washing, and surface modification methods to suppress or improve this issue. For example, patent CN113764647A discloses a ternary cathode material co-doped with Zr and multiple anions, its preparation method, and a lithium-ion battery. It uses various combinations of zirconium and fluorine, chlorine, and sulfur, employing a co-precipitation method to prepare the corresponding ternary precursor, and then using a high-temperature solid-state method to prepare the corresponding ternary cathode material. Because the atmosphere used in the preparation of the ternary cathode material is oxidizing, the S declared in this patent... 2- As a multi-anion source, this method contains theoretical errors. Patent CN114162881A discloses a method for improving ternary cathode materials with fluorine doping. It employs a co-precipitation method to precipitate fluorine into the precursor during precursor preparation, then mixes this precursor with a lithium source, and finally obtains the fluorine-doped ternary cathode material via a high-temperature solid-state method. While fluorine doping can suppress oxygen evolution in ternary cathode materials to some extent, fluorine has a high corrosiveness to equipment. Furthermore, the co-precipitation method used in this patent results in a relatively uniform distribution of fluorine, leading to a severe deterioration in the material's energy density while improving the oxygen evolution problem. Summary of the Invention

[0004] To address the shortcomings of existing lithium-ion high-nickel ternary cathode materials, such as oxygen release and severe side reactions with the electrolyte, leading to poor lifespan and cycle performance, this invention provides a long-cycle high-nickel ternary cathode material and its preparation method. This invention uses sulfides or elemental sulfur to partially replace oxygen in the shallow surface layer of the high-nickel ternary cathode material through grinding or heating, thereby reconstructing the shallow surface layer and achieving the aforementioned improvements.

[0005] In a first aspect, the present invention provides a high-nickel ternary cathode material. According to an embodiment of the present invention, the oxygen in the shallow surface layer of the high-nickel ternary cathode material is replaced by anionic sulfur. The high-nickel ternary cathode material according to the embodiment of the present invention has a long lifespan and good cycle performance.

[0006] In another aspect, the present invention provides a method for preparing a high-nickel ternary cathode material. According to an embodiment of the present invention, the method includes:

[0007] 1) The high-nickel ternary cathode material to be treated is mixed with a sulfur source to obtain a mixture;

[0008] 2) The mixture is ground or heated to obtain the high-nickel ternary cathode material. The high-nickel ternary cathode material obtained according to the method of this embodiment has a long lifespan and good cycle performance.

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

[0010] According to embodiments of the present invention, the sulfur source is elemental sulfur or a sulfide. The present invention uses sulfides or elemental sulfur to partially replace oxygen in the shallow surface layer of the high-nickel ternary cathode material through grinding or heating, thereby reconstructing the shallow surface layer of the high-nickel ternary cathode material and achieving the aforementioned improvements.

[0011] According to embodiments of the present invention, the sulfide includes one or more selected from zinc disulfide, carbon disulfide, molybdenum disulfide, lithium sulfide, phosphorus pentasulfide, and ammonium sulfide.

[0012] According to an embodiment of the present invention, the mass ratio of the sulfur source to the high-nickel ternary cathode material to be treated is 1000 to 3000 ppm, wherein the sulfur source is measured in terms of elemental sulfur.

[0013] According to an embodiment of the present invention, the temperature of the heat treatment is 100-150°C.

[0014] According to an embodiment of the present invention, the heat treatment time is 6 to 10 hours.

[0015] According to an embodiment of the present invention, the heat treatment further includes cooling the heat-treated material to room temperature and then crushing and sieving it.

[0016] In another aspect, the present invention also proposes a high-nickel ternary cathode material. According to an embodiment of the present invention, the high-nickel ternary cathode material is prepared according to the method described above.

[0017] In another aspect, the present invention also provides a battery. According to an embodiment of the present invention, the battery comprises the high-nickel ternary cathode material described above or the high-nickel ternary cathode material prepared according to the method described above.

[0018] According to an embodiment of the present invention, sulfide ions belong to Lewis bases and can absorb hydrogen fluoride generated in the electrolyte to a certain extent, thereby inhibiting the corrosion of the high-nickel ternary cathode material surface by hydrogen fluoride, thus improving the cycle life of the ternary cathode material. At the same time, sulfide ions replace some oxygen ions in the shallow surface layer of the high-nickel ternary cathode material particles, causing the shallow surface layer of the ternary cathode material to be reconstructed. This effectively inhibits oxygen release from the surface of the high-nickel ternary cathode material and the structural collapse caused by oxygen release, thereby improving the gas generation problem and cycle life problem of the high-nickel cathode material. Attached Figure Description

[0019] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0020] Figure 1 This refers to the cycle discharge capacity of a button battery according to an embodiment of the present invention. Detailed Implementation

[0021] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0022] Example 1

[0023] A certain amount of high-nickel ternary cathode material (nickel molar content ratio of Ni / (Ni+Co+Mn)≥0.8) and ammonium sulfide were weighed out, with the mass ratio of sulfur in ammonium sulfide to that in high-nickel ternary cathode material being 2000 ppm. The two materials were then mixed evenly, and the mixture was heat-treated at 130℃ for 8 hours in an inert atmosphere. Finally, the heat-treated material was cooled to room temperature and subjected to crushing and sieving in a temperature-controlled environment to obtain anion-modified high-nickel ternary cathode material.

[0024] Example 2

[0025] A certain amount of high-nickel ternary cathode material (nickel molar content ratio of Ni / (Ni+Co+Mn)≥0.8) and ammonium sulfide were weighed out, with the mass ratio of sulfur in ammonium sulfide to that in high-nickel ternary cathode material being 3000 ppm. The two materials were then mixed evenly, and the mixture was heat-treated at 100℃ for 15 hours in an inert atmosphere. Finally, the heat-treated material was cooled to room temperature and subjected to crushing and sieving in a temperature-controlled environment to obtain anion-modified high-nickel ternary cathode material.

[0026] Example 3

[0027] A certain amount of high-nickel ternary cathode material (nickel molar content ratio of Ni / (Ni+Co+Mn)≥0.8) and ammonium sulfide were weighed out, with the mass ratio of sulfur in ammonium sulfide to that in high-nickel ternary cathode material being 1000ppm. The two materials were then mixed evenly, and the mixture was heat-treated at 150℃ for 6 hours in an inert atmosphere. Finally, the heat-treated material was cooled to room temperature and subjected to crushing and sieving in a temperature-controlled environment to obtain anion-modified high-nickel ternary cathode material.

[0028] Comparative Example 1

[0029] A certain amount of high-nickel ternary cathode material (nickel molar content ratio of Ni / (Ni+Co+Mn)≥0.8) is weighed and subjected to crushing and sieving in a temperature-controlled environment.

[0030] Comparative Example 2

[0031] A certain amount of high-nickel ternary cathode material (nickel molar content ratio of Ni / (Ni+Co+Mn)≥0.8) was weighed, and then the high-nickel ternary cathode material was heat-treated at 130℃ for 8 hours in an inert atmosphere. Finally, the heat-treated material was cooled to room temperature and then crushed and sieved in a temperature-controlled environment.

[0032] Button Battery Preparation: The positive electrode materials obtained in Examples 1-2 and Comparative Examples 1-2 were assembled into button batteries, as follows: Positive electrode material, conductive agent (acetylene black), and binder (PVDF) were weighed in a mass ratio of 90%:5%:5%. The weighed positive electrode material and acetylene black were mixed and ground in an agate mortar. After grinding evenly, the mixture was added to N-methylpyrrolidone (NMP), which had fully reacted with PVDF, and ground continuously until the slurry became a viscous liquid with a certain fluidity. The ground slurry was evenly transferred onto aluminum foil, and the sample was evenly coated using a 300 μm thick coater. It was then pre-baked in air at 60°C for 5 hours, followed by vacuum drying at 90°C for 12 hours to remove water and organic matter from the coated sample. Electrode sheets were then cut to size for later use, yielding the positive electrode sheet.

[0033] Using lithium foil as the negative electrode and a prepared electrode sheet as the positive electrode, with an electrolyte ratio of EC:DMC = 1:1, a coin cell battery was assembled and tested using a BTV charge-discharge tester. At 25℃, the lithium-ion battery assembled with the above positive electrode sheet underwent 0.5C / 1C charge-discharge cycles at an operating voltage of 3.0-4.3V. The cycle discharge capacity curve of the coin cell battery is shown below. Figure 1 ,from Figure 1As can be seen, the cycle improvement of Examples 1 and 2 is very obvious compared with Comparative Example 1, and the dry coating cycle of Comparative Example 2 is also significantly improved.

[0034] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0035] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A high-nickel ternary cathode material, characterized in that, The oxygen in the shallow surface layer of the high-nickel ternary cathode material is replaced by anionic sulfur. The preparation method of the high-nickel ternary cathode material includes: 1) The high-nickel ternary cathode material to be treated is mixed with a sulfur source to obtain a mixture; 2) The mixture is heated to obtain the high-nickel ternary cathode material; The temperature of the heat treatment is 100~150℃, and the time of the heat treatment is 6~10h; The mass ratio of the sulfur source to the high-nickel ternary cathode material to be treated is 1000~3000ppm, wherein the sulfur source is measured in terms of elemental sulfur.

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

8.

3. The high-nickel ternary cathode material according to claim 1, characterized in that, The sulfur source is elemental sulfur or a sulfide.

4. The high-nickel ternary cathode material according to claim 3, characterized in that, The sulfide includes one or more selected from zinc disulfide, carbon disulfide, molybdenum disulfide, lithium sulfide, phosphorus pentasulfide, and ammonia sulfide.

5. The high-nickel ternary cathode material according to claim 1, characterized in that, The heat treatment further includes cooling the heat-treated material to room temperature and then crushing and sieving it.

6. A battery, characterized in that, The battery comprises the high-nickel ternary cathode material as described in any one of claims 1-5.

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