Lithium-rich manganese-based positive electrode material grain reconstruction method

Abstract

The invention discloses a grain reconstruction method for a lithium-rich manganese-based positive electrode material. The chemical formula of the lithium-rich manganese-based positive electrode material is Li1. 2NixMnyCozO2, n is greater than 0 and less than or equal to 1.2, 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 is equal to 0.8. The preparation method comprises the following steps: (1) adding 10g of the lithium-rich manganese-based positive electrode material and a certain mass fraction of nickel, cobalt and manganese salts into a 100ml beaker, adding 50ml of deionized water, and stirring for 2-6 hours; (2) putting the beaker on a heating table, evaporating to dryness at 60-150 DEG C, and then transferring into an oven at 60 DEG C for overnight drying; and (3) uniformly grinding the dried powder and a certain amount of lithium salt, putting into a muffle furnace, calcining at a high temperature of 400-1000 DEG C for 5-20 hours, and cooling to obtain the lithium-rich manganese-based positive electrode material with reconstructed crystal grains. The crystalline grains of the lithium-rich manganese-based positive electrode material are reconstructed through a solvothermal method; according to the process, the cost of used equipment is low, the preparation process is simple, the repeatability is good, and the lithium-rich manganese-based positive electrode material with reconstructed crystal grains can be obtained by regulating and controlling the mass fraction of the nickel-cobalt-manganese salt and the calcination temperature.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery materials, and in particular relates to a method for reconstructing grains of lithium-rich manganese-based positive electrode materials. Background Art

[0002] As problems such as the burning of fossil fuels and environmental pollution become increasingly prominent, the development of green and renewable energy has become a key area of ​​development and direction for various countries. New energy sources such as solar energy, wind energy, and tidal energy have the characteristics of being green and renewable, and have become the main force in the field of new energy. However, these materials have disadvantages such as discontinuity and regionality, and require energy storage equipment to store the energy they generate and release it when needed. Batteries are devices that convert chemical energy into electrical energy. In the battery system, lithium-ion batteries have become a hot research field, and various lithium storage materials have been widely studied for use as secondary lithium-ion batteries. The energy density and performance of lithium batteries are mainly determined by the performance of the positive electrode material.

[0003] Among all the cathode materials studied so far, lithium-rich manganese-based cathode materials have excellent discharge capacity (>280 mAh g -1 ), high operating voltage, low cost, good safety and other advantages and is considered to be one of the most promising next-generation commercial cathode materials. Although lithium-rich manganese-based cathode materials show excellent energy density, they have problems such as low initial coulombic efficiency, poor rate performance and voltage / capacity decay, which seriously restrict their commercialization process. The grown grains of lithium-rich manganese-based cathode materials can reduce the grain boundary transmission impedance and improve the lithium-rich layered material Li + The diffusion dynamics of the lithium-rich manganese-based cathode material are improved, and the reduction in specific surface area effectively inhibits the occurrence of side reactions with the electrolyte, effectively improving the structural stability and electrochemical performance of the lithium-rich manganese-based cathode material. Therefore, the present invention can obtain a lithium-rich manganese-based cathode material with grain reconstruction by regulating the mass fraction of the added nickel-cobalt-manganese salt and the calcination temperature. Summary of the Invention

[0004] The present invention uses a solvothermal method to restructure the grains of a lithium-rich manganese-based cathode material. By adjusting the mass fraction of the added nickel-cobalt-manganese salt and the calcination temperature, a restructured lithium-rich manganese-based cathode material can be obtained. The resulting material has a simple preparation process and good reproducibility.

[0005] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0006] Material, the chemical formula of the lithium-rich manganese-based positive electrode material is: Li 1.2 Ni x Mn y Co zO2, 0<n≤1.2, 0≤x≤0.6, 0≤y≤0.6, 0≤z≤0.2 and x+y+z=0.8. The preparation method thereof comprises the following steps:

[0007] (1) Take 10g of lithium-rich manganese-based cathode material and a certain mass fraction of nickel, cobalt, and manganese salts and add them to a 100ml beaker, add 50ml of deionized water, and stir for 2-6h;

[0008] (2) Place the beaker on a heating table and evaporate to dryness at 60-150°C, then transfer to a 60°C oven to dry overnight;

[0009] (3) After the dried powder is evenly ground with a certain amount of lithium salt, it is placed in a muffle furnace and calcined at a high temperature of 400-1000°C for 5-20 hours. After cooling, a lithium-rich manganese-based positive electrode material with reconstructed grains can be obtained.

[0010] Preferably, the nickel, cobalt and manganese salts in step (1) are one or more of sulfate, nitrate and acetate.

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

[0012] Preferably, the stirring time in step (1) is 2-6 hours.

[0013] More preferably, the stirring time in step (1) is 4 h.

[0014] Preferably, the heating temperature of the heating stage in step (2) is 60-150°C.

[0015] More preferably, the oven heating temperature in step (2) is 120°C.

[0016] Preferably, in step (3), the calcination temperature is 400-1000° C., and the calcination time is 5-20 h.

[0017] More preferably, the calcination temperature in step (3) is 400-700° C., and the calcination time is 10-20 h.

[0018] Beneficial effects

[0019] The present invention prepares a lithium-rich manganese-based positive electrode material with grain reconstruction by a solvent thermal method, with a particle size of 2-7 μm and a 0.1C discharge capacity of the prepared material of 270-320 mAh g -1 The capacity retention rate after 100 cycles at a rate of 1C is higher than 85%. The process of the present invention has low equipment cost, simple preparation process, good repeatability, and can obtain a lithium-rich manganese-based positive electrode material with reconstructed grains by adjusting the mass fraction of the added nickel-cobalt-manganese salt and the calcination temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 SEM image of the sample in Example 1;

[0021] Figure 2 The first cycle charge and discharge curve of the sample in Example 1;

[0022] Figure 3 SEM image of the sample in Example 2;

[0023] Figure 4 Cycle diagram of sample 1C in Example 2;

[0024] Figure 5 SEM image of the sample in Example 3 DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be further described below with reference to specific embodiments, but is not limited thereto.

[0026] Example 1

[0027] Step 1. Take 10g of lithium-rich manganese-based cathode material powder and add it to a 100ml beaker. Add 50ml of deionized water. Then weigh sulfate (nickel sulfate + cobalt sulfate + manganese sulfate) with a mass ratio of 100:1 to the cathode powder and add it to the beaker. Stir magnetically for 4h.

[0028] Step 2. Place the beaker on a heating plate and evaporate to dryness at 120°C, then transfer to a 60°C oven to dry overnight.

[0029] Step 3. Weigh lithium carbonate with a molar ratio of 1.5:1 to sulfate (nickel sulfate + cobalt sulfate + manganese sulfate) and grind evenly. Place the mixture in a muffle furnace and calcine at 500°C for 10 hours. After cooling, a lithium-rich manganese-based positive electrode material with reconstructed grains can be obtained.

[0030] Figure 1 This is a SEM image of the reconstructed Li-rich manganese-based cathode material after heating at 500°C for 10 hours. As can be seen from the image, the material still maintains a spherical morphology with a particle size of 3.1 μm.

[0031] Figure 2 The first cycle charge-discharge curve of the grain-reconstructed lithium-rich manganese-based cathode material obtained after being heated at 500°C for 10 hours at a rate of 0.1C. The first charge capacity is 336.8 mAh g -1 The first discharge capacity is 290.13 mAh g -1 , the first cycle Coulomb efficiency is 86.14%

[0032] Example 2

[0033] Step 1. Take 10g of lithium-rich manganese-based cathode material powder and add it to a 100ml beaker. Add 50ml of deionized water. Then weigh sulfate (nickel sulfate + cobalt sulfate + manganese sulfate) with a mass ratio of 100:10 to the cathode powder and add it to the beaker. Stir magnetically for 4h.

[0034] Step 2. Place the beaker on a heating plate and evaporate to dryness at 120°C, then transfer to a 60°C oven to dry overnight.

[0035] Step 3. Weigh lithium carbonate with a molar ratio of 1.5:1 to sulfate (nickel sulfate + cobalt sulfate + manganese sulfate) and grind it evenly. Place the mixture in a muffle furnace and calcine it at 600°C for 12 hours. After cooling, a lithium-rich manganese-based positive electrode material with reconstructed grains can be obtained.

[0036] Figure 3 This is a SEM image of the reconstructed Li-rich manganese-based cathode material after heating at 600°C for 12 hours. As can be seen from the image, the material still maintains a spherical morphology with a particle size of 3.5μm.

[0037] Figure 4 The cycling diagram of the reconstructed lithium-rich manganese-based cathode material obtained after heating at 600°C for 12 hours at a rate of 1C. The first cycle discharge capacity is 230.8 mAh g -1 , after 100 cycles, there is still a capacity retention rate of 87.88%.

[0038] Example 3

[0039] Step 1. Take 10g of lithium-rich manganese-based cathode material powder and add it to a 100ml beaker. Add 50ml of deionized water. Then weigh sulfate (nickel sulfate + cobalt sulfate + manganese sulfate) with a mass ratio of 100:20 to the cathode powder and add it to the beaker. Stir magnetically for 4h.

[0040] Step 2. Place the beaker on a heating plate and evaporate to dryness at 120°C, then transfer to a 60°C oven to dry overnight.

[0041] Step 3. Weigh lithium carbonate with a molar ratio of 1.5:1 to sulfate (nickel sulfate + cobalt sulfate + manganese sulfate) and grind evenly. Place the mixture in a muffle furnace and calcine at 700°C for 15 hours. After cooling, a lithium-rich manganese-based positive electrode material with reconstructed grains can be obtained.

[0042] Figure 5 This is an SEM image of the reconstructed Li-rich manganese-based cathode material after heating at 700°C for 15 hours. As can be seen from the image, the material still maintains a spherical morphology with a particle size of 4.2 μm.

[0043] It should be noted that the above embodiments are only some of the embodiments for implementing the preferred methods of the present invention, and are not all of the embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work should fall within the scope of protection of the present invention.

Claims

1. A method for reconstructing grains of lithium-rich manganese-based positive electrode materials, characterized in that: The chemical formula of the lithium-rich manganese-based positive electrode 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 reconstructing grains of the lithium-rich manganese-based cathode material according to claim 1, characterized in that: The following steps are involved: (1) Take 10g of lithium-rich manganese-based cathode material and a certain mass fraction of nickel, cobalt, and manganese salts and add them to a 100ml beaker, add 50ml of deionized water, and stir for 2-6h; (2) Place the beaker on a heating table and evaporate to dryness at 60-150°C, then transfer to a 60°C oven to dry overnight; (3) After the dried powder is evenly ground with a certain amount of lithium salt, it is placed in a muffle furnace and calcined at a high temperature of 400-1000°C for 5-20 hours. After cooling, a lithium-rich manganese-based positive electrode material with reconstructed grains can be obtained.

3. The method for reconstructing grains of lithium-rich manganese-based cathode materials according to claim 2, characterized in that: In step (1), the nickel, cobalt and manganese salts are one or more of sulfate, nitrate and acetate.

4. The method for reconstructing grains of lithium-rich manganese-based cathode materials according to claim 2, characterized in that: The stirring time in step (1) is 2-6h.

5. The method for reconstructing grains of lithium-rich manganese-based positive electrode materials according to claim 22, characterized in that: The heating temperature in step (2) is 60-150°C.

6. The method for reconstructing grains of a lithium-rich manganese-based cathode material according to claim 22, characterized in that: In step (3), the calcination temperature is 400-1000° C., and the calcination time is 50-20 h.

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