Method for constructing epitaxial entropy coating layer of lithium-rich manganese-based positive electrode material

Abstract

The invention discloses a construction method of an epitaxial entropy coating layer of a lithium-rich manganese-based positive electrode material. The chemical formula of the lithium-rich manganese-based positive electrode material is Li1. 5NixMnyCozO2.5, x is greater than or equal to 0 and less than or equal to 0.6, y is greater than or equal to 0 and less than or equal to 0.6, z is greater than or equal to 0 and less than or equal to 0.2, and x + y + z = 1. The preparation method comprises the following steps: (1) putting nickel, cobalt and manganese salts in a certain molar ratio into a muffle furnace, and sintering at a high temperature of 200-500 DEG C for 2-10 hours to remove crystal water; (2) adding the nickel salt, the cobalt salt and the manganese salt from which the crystal water is removed into a ball milling tank, carrying out ball milling for 2-6 hours at the rotating speed of 200-500rpm, then putting the ground powder into a crucible, transferring the crucible into a muffle furnace, carrying out high-temperature calcination for 2-10 hours at the temperature of 200-700 DEG C, and cooling to obtain a coating material; and (3) uniformly mixing the prepared lithium-rich manganese-based positive electrode material and a coating material according to a certain mass ratio, putting the mixture into a muffle furnace, calcining at a high temperature of 400-1000 DEG C for 5-20 hours, and cooling to obtain the epitaxial entropy coated lithium-rich manganese-based positive electrode material. The epitaxial entropy coating layer of the lithium-rich manganese-based positive electrode material is constructed through a solid phase method and a high-temperature calcination method; according to the method, the cost of equipment used in the process is low, the preparation process is simple, the repeatability is good, and the epitaxial entropy coating layer lithium-rich manganese-based positive electrode materials with different thicknesses can be obtained by regulating and controlling the proportion of the coating material.

Description

Technical Field

[0001] This invention belongs to the field of battery materials technology, specifically relating to a method for constructing an epitaxial entropy coating layer for lithium-rich manganese-based cathode materials. Background Technology

[0002] With the increasing prominence of problems such as fossil fuel combustion and environmental pollution, the development of green and renewable energy has become a key area and direction for development in various countries. Solar, wind, and tidal energy, among other new energy sources, possess characteristics such as being green and renewable, making them the mainstay of the new energy field. However, these materials have drawbacks such as discontinuity and geographical limitations, requiring energy storage devices to store the energy they generate and release it when needed. Batteries are devices that convert chemical energy into electrical energy. In battery systems, lithium-ion batteries have become the preferred device for large-scale energy storage applications such as electric vehicles and smart grids. Higher energy density is a prerequisite for their large-scale application, and in lithium-ion batteries, energy density is largely determined directly by the cathode material.

[0003] Among all the cathode materials currently studied, lithium-rich manganese-based cathode materials exhibit the best discharge specific capacity (>280 mAh g⁻¹). -1 Lithium-rich manganese-based cathode materials are considered one of the most promising next-generation commercial cathode materials due to their advantages such as high operating voltage, low cost, and good safety. Research shows that the high discharge specific capacity of this material mainly originates from the irreversible oxidation of lattice oxygen during the electrochemical reaction. However, while the irreversible oxidation of lattice oxygen brings ultra-high discharge specific capacity, it also causes capacity and voltage decay during cycling, thus severely affecting the further application of lithium-rich manganese-based cathode materials. Therefore, this invention constructs an epitaxial entropy-coated lithium-rich manganese-based cathode material using a solid-state method. The epitaxial entropy coating not only reduces side reactions with the electrolyte, improving the structural stability and electrochemical performance of the lithium-rich manganese-based cathode material, but also acts as a fast ion conductor, accelerating the lithium-ion transport rate and thus improving the rate performance of the lithium-rich manganese-based cathode material. Summary of the Invention

[0004] This invention constructs an epitaxial entropy coating layer for lithium-rich manganese-based cathode materials using a solid-state method and a high-temperature calcination method. Based on this, lithium-rich manganese-based cathode materials with epitaxial entropy coating layers of different thicknesses can be obtained by adjusting the proportion of the coating material. The preparation process of the obtained materials is simple and has good reproducibility.

[0005] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0006] The material, the chemical formula of the lithium-rich manganese-based cathode material is: Li 1.5 Ni x Mn y Co z O2.5 The conditions are: 0 ≤ x ≤ 0.6, 0 ≤ y ≤ 0.6, 0 ≤ z ≤ 0.2, and x + y + z = 1. The preparation method includes the following steps:

[0007] (1) A certain molar ratio of nickel, cobalt and manganese salts are placed in a muffle furnace and sintered at a high temperature of 200-500℃ for 2-10 hours to remove the water of crystallization;

[0008] (2) Add the dehydrated nickel, cobalt and manganese salts to a ball mill jar and ball mill at 200-500 rpm for 2-6 hours. Then put the ground powder into a crucible and transfer it to a muffle furnace for high-temperature calcination at 200-700℃ for 2-10 hours. After cooling, the coating material is obtained.

[0009] (3) The prepared lithium-rich manganese-based cathode material and the coating material are mixed evenly according to a certain mass ratio, and placed in a muffle furnace for high-temperature calcination at 400-1000℃ for 5-20h. After cooling, the lithium-rich manganese-based cathode material with epitaxial entropy coating layer can be obtained.

[0010] Preferably, in step (1), the nickel, cobalt, and manganese salts are one or more of sulfates, nitrates, and acetates.

[0011] More preferably, the nickel, cobalt, and manganese salts are acetates.

[0012] Preferably, the calcination temperature in the muffle furnace in step (1) is 200-500℃ and the calcination time is 2-10h.

[0013] More preferably, in step (1), the calcination temperature in the muffle furnace is 300°C and the calcination time is 5 hours.

[0014] Preferably, in step (2), the rotation speed is 200-600 rpm and the ball milling time is 2-6 h.

[0015] More preferably, in step (2), the rotation speed is 300 rpm and the ball milling time is 5 h.

[0016] Preferably, the calcination temperature in step (2) is 200-700℃ and the calcination time is 2-10h.

[0017] More preferably, the calcination temperature in step (2) is 200-500℃ and the calcination time is 5-10h.

[0018] Preferably, the calcination temperature in step (3) is 400-1000℃ and the calcination time is 5-20h.

[0019] More preferably, the calcination temperature in step (3) is 500-800℃ and the calcination time is 10-20h.

[0020] Beneficial effects

[0021] This invention prepares epitaxial entropy-coated lithium-rich manganese-based cathode materials via solid-state and high-temperature calcination methods. The epitaxial entropy coating not only reduces side reactions with the electrolyte, improving the structural stability and electrochemical performance of the lithium-rich manganese-based cathode material, but also acts as a fast ion conductor, accelerating lithium-ion transport and thus improving the rate performance. SEM and charge-discharge tests revealed that the secondary particles of the epitaxial entropy-coated lithium-rich manganese-based cathode material maintain a spherical morphology with a particle size between 3-7 μm, and a uniform epitaxial entropy coating layer is observed. Furthermore, the epitaxial entropy-coated lithium-rich manganese-based cathode material exhibits a discharge specific capacity of 260-300 mAh g⁻¹ at 0.1C. -1 At 1C rate, the capacity retention rate is higher than 80% after 200 cycles. The process of this invention has low equipment cost, simple preparation process, good repeatability, and lithium-rich manganese-based cathode materials with epitaxial entropy coating of different thicknesses can be obtained by adjusting the proportion of coating material. Attached Figure Description

[0022] Figure 1 SEM image of the sample in Example 1;

[0023] Figure 2 The first charge-discharge curve of the sample in Example 1;

[0024] Figure 3 SEM images of the samples in Example 2;

[0025] Figure 4 Cyclic diagram of sample 1C at magnification in Example 2;

[0026] Figure 5 SEM images of samples in Example 3 Detailed Implementation

[0027] The technical solution of the present invention will be further described below with reference to specific embodiments, but it is not limited thereto.

[0028] Example 1

[0029] Step 1. Place nickel, cobalt, and manganese salts with a molar ratio of 0.1625:0.1625:0.675 into a muffle furnace and sinter at 300°C for 5 hours to remove water of crystallization;

[0030] Step 2. Add the dehydrated nickel, cobalt and manganese salts to a ball mill jar and ball mill at 300 rpm for 5 hours. Then put the ground powder into a crucible and transfer it to a muffle furnace for high-temperature calcination at 400°C for 6 hours. After cooling, the coating material is obtained.

[0031] Step 3. Mix the prepared lithium-rich manganese-based cathode material and the coating material at a mass ratio of 100:1, place them in a muffle furnace and calcine at 500℃ for 8 hours. After cooling, the lithium-rich manganese-based cathode material with an epitaxial entropy coating layer can be obtained.

[0032] Figure 1 The image shows the SEM image of the lithium-rich manganese-based cathode material with epitaxial entropy coating obtained after holding at 500℃ for 8 hours. As can be seen from the image, the material still maintains a spherical morphology with a particle size of 3.1 μm, indicating that a small amount of epitaxial entropy coating does not affect the morphology of the lithium-rich manganese-based cathode material.

[0033] Figure 2 The image shows the first charge-discharge curve of the epitaxial entropy-coated lithium-rich manganese-based cathode material obtained after holding at 500℃ for 8 hours at a 0.1C rate. The first charge specific capacity is 361.05 mAh g. -1 The initial discharge specific capacity was 276.81 mAh g. -1 The first lap efficiency for Cullen was 76.67%.

[0034] Example 2

[0035] Step 1. Place nickel, cobalt, and manganese salts with a molar ratio of 0.1625:0.1625:0.675 into a muffle furnace and sinter at 300°C for 5 hours to remove water of crystallization;

[0036] Step 2. Add the dehydrated nickel, cobalt and manganese salts to a ball mill jar and ball mill at 300 rpm for 5 hours. Then put the ground powder into a crucible and transfer it to a muffle furnace for high-temperature calcination at 500°C for 6 hours. After cooling, the coating material is obtained.

[0037] Step 3. Mix the prepared lithium-rich manganese-based cathode material and the coating material at a mass ratio of 100:10, place them in a muffle furnace and calcine at 800℃ for 10 hours. After cooling, the lithium-rich manganese-based cathode material with an epitaxial entropy coating layer can be obtained.

[0038] Figure 3 The image shows the SEM image of the epitaxial entropy-coated lithium-rich manganese-based cathode material obtained after holding at 800℃ for 10 h. The image shows that the material maintains a spherical morphology with a particle size of 3.5 μm, and the coating material is uniformly attached to the surface of the lithium-rich manganese-based cathode material. Furthermore, the reduced gaps between primary particles lower the barrier to lithium-ion grain boundary transport, thereby improving the lithium-ion transport rate of the lithium-rich manganese-based cathode material.

[0039] Figure 4 This is a cycling diagram of the epitaxial entropy-coated lithium-rich manganese-based cathode material obtained after holding at 800℃ for 10 hours at 1C rate. The first discharge specific capacity is 200.1 mAh g.-1 After 200 cycles, it still retains 90.95% of its capacity.

[0040] Example 3

[0041] Step 1. Place nickel, cobalt, and manganese salts with a molar ratio of 0.3:0.1:0.6 into a muffle furnace and sinter at 300°C for 5 hours to remove water of crystallization;

[0042] Step 2. Add the dehydrated nickel, cobalt and manganese salts to a ball mill jar and ball mill at 300 rpm for 5 hours. Then put the ground powder into a crucible and transfer it to a muffle furnace for high-temperature calcination at 300°C for 5 hours. After cooling, the coating material is obtained.

[0043] Step 3. Mix the prepared lithium-rich manganese-based cathode material and the coating material at a mass ratio of 100:20, place them in a muffle furnace and calcine at 500℃ for 8 hours. After cooling, the lithium-rich manganese-based cathode material with epitaxial entropy coating layer can be obtained.

[0044] Figure 5 The image shows the SEM image of the epitaxial entropy-coated lithium-rich manganese-based cathode material obtained after holding at 900℃ for 15 h. As can be seen from the image, the material maintains a spherical morphology with a particle size of 5.8 μm, which is much larger than that of the uncoated lithium-rich manganese-based cathode material. This is likely due to the excessively thick coating layer adhering to the material surface.

[0045] It should be noted that the above embodiments are merely some embodiments of preferred embodiments of the present invention, and not all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

Claims

1. A method for constructing an epitaxial entropy coating layer for a lithium-rich manganese-based cathode material, characterized in that, The chemical formula of the lithium-rich manganese-based cathode material is: Li 1.2 Ni x Mn y Co z O2, 0<n≤1.2, 0≤x≤0.6, 0≤y≤0.6, 0≤z≤0.2 and x+y+z=0.

8.

2. A method for constructing the epitaxial entropy coating layer of the lithium-rich manganese-based cathode material according to claim 1, characterized in that, Includes the following steps: (1) A certain molar ratio of nickel, cobalt and manganese salts are placed in a muffle furnace and sintered at a high temperature of 200-500℃ for 2-10 hours to remove the water of crystallization; (2) Add the dehydrated nickel, cobalt and manganese salts to a ball mill jar and ball mill at 200-600 rpm for 2-6 hours. Then put the ground powder into a crucible and transfer it to a muffle furnace for high-temperature calcination at 200-700℃ for 2-10 hours. After cooling, the coating material is obtained. (3) The prepared lithium-rich manganese-based cathode material and the coating material are mixed evenly according to a certain mass ratio, and placed in a muffle furnace for high-temperature calcination at 400-1000℃ for 5-20h. After cooling, the lithium-rich manganese-based cathode material with epitaxial entropy coating layer can be obtained.

3. The method for constructing the epitaxial entropy coating layer of the lithium-rich manganese-based cathode material according to claim 2, characterized in that, In step (1), the nickel, cobalt, and manganese salts are one or more of sulfates, nitrates, and acetates.

4. The method for constructing the epitaxial entropy coating layer of the lithium-rich manganese-based cathode material according to claim 2, characterized in that, In step (1), the calcination temperature in the muffle furnace is 200-500℃ and the calcination time is 2-10h.

5. The method for constructing the epitaxial entropy coating layer of the lithium-rich manganese-based cathode material according to claim 22, characterized in that, In step (2), the rotation speed is 200-600 rpm and the ball milling time is 2-6 hours.

6. The method for constructing the epitaxial entropy coating layer of the lithium-rich manganese-based cathode material according to claim 22, characterized in that, In step (2), the calcination temperature is 200-700℃ and the calcination time is 2-10h.

7. The method for constructing the epitaxial entropy coating layer of the lithium-rich manganese-based cathode material according to claim 22, characterized in that, In step (3), the calcination temperature is 400-1000℃ and the calcination time is 5-20h.

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