A positive electrode lithium supplement material and its preparation method and application

Abstract

The present invention discloses a positive electrode lithium replenisher material and a preparation method and application thereof. The preparation method comprises: mixing and reacting Li2NiO2 in a specific atmosphere under a specific environment to obtain a Li2NiO2 positive electrode lithium replenisher material with a core-shell structure, wherein the core is Li2NiO2 and the shell is the reaction product Li3N. In the present invention, the positive electrode lithium replenisher can generate Li3N on the surface in a specific environment. Li3N isolates the reaction between moisture and the inner layer lithium replenisher, solves the problem that the positive electrode lithium replenisher material is sensitive to moisture, improves the environmental stability of the material, and avoids the occurrence of gelation. At the same time, lithium nitride has a high theoretical specific capacity, and a small amount of addition can achieve an improvement in the coulomb efficiency of the battery in the first week. At the same time, the safety performance and coulomb efficiency of the battery can be improved.

Description

Technical Field

[0001] The present invention belongs to the field of lithium-ion batteries, and in particular relates to a positive electrode lithium supplement material and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries have become energy storage devices that have attracted much attention due to their outstanding advantages such as high operating voltage, high specific energy, large capacity, long service life, light weight, and small size. In recent years, the rapid development and market growth of mobile devices and electric vehicles have led to a strong demand for low-cost, small-size, lightweight, and high-energy-density secondary batteries (e.g., lithium-ion batteries). The most studied and used lithium battery is a carbon-based negative electrode lithium-ion battery. Although it has many advantages mentioned above, there is a problem that nearly 5-20% (if it is a new negative electrode such as silicon carbon, this proportion is even greater) of the lithium ions extracted from the positive electrode are consumed in the solid electrolyte interface layer (SEI) formed on the surface of the negative electrode. Because this process is irreversible, that is, the loss of lithium ions is irreversible, which directly leads to low first-cycle coulomb efficiency of the battery and partial irreversible capacity loss; for this problem, it is currently recognized in academia and industry that compensating for the irreversible loss of lithium ions by replenishing lithium can restore the capacity of the positive electrode and greatly improve the energy density of lithium-ion batteries.

[0003] Positive electrode lithium replenishment is generally done during the slurrying process of lithium battery production. The positive electrode lithium replenisher and the positive electrode material are added at the same time according to the energy density ratio that needs to be increased. The positive electrode lithium replenisher will release lithium ions during the first charging process to compensate for the irreversible capacity loss caused by the formation of the SEI film on the negative electrode surface. Positive electrode lithium replenishment has better industrial application prospects due to its simple operation, high process safety and high compatibility with existing battery production processes.

[0004] CN11249049A discloses a method of directly mixing Li2NiO2 in the positive electrode slurry, which can compensate for the irreversible capacity loss to a certain extent, but it is easy to react with moisture in the air to cause the PVDF in the positive electrode slurry to be deactivated, resulting in the positive electrode slurry being in a gel state and unable to be coated, which is harmful to the use of the positive electrode material and the safety of the battery. CN114242939A discloses Al surface doping of Li2NiO2, which can improve the structural stability and thermal stability of the material, while preventing HF in the electrolyte from corroding the active material, reducing the surface impedance and improving the cycle performance. However, its process is relatively complicated and cannot meet the requirements of industrial production.

[0005] The residual lithium on the surface of Li2NiO2 materials, the difficulty in processing, and the improvement of their easy side reactions with electrolytes to produce gas, dissolution at the negative electrode and poor conductivity are technical problems that urgently need to be solved in the field of lithium-ion battery technology. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention provides a positive electrode lithium replenisher material and a preparation method and application thereof, which utilizes N2 to react with Li2NiO2 in a high temperature environment to generate Li3N, thereby solving the problem that the current positive electrode lithium replenisher material is sensitive to moisture, improving the environmental stability of the material, and avoiding the occurrence of gelation of the positive electrode lithium replenisher material after being added to the positive electrode slurry, thereby improving the safety performance of the battery.

[0007] The present invention is achieved through the following technical solutions:

[0008] A method for preparing a positive electrode lithium supplement material, comprising:

[0009] Under a specific atmosphere, the positive electrode lithium replenisher Li2NiO2 is mixed with nitrogen to react to obtain a positive electrode lithium replenisher material.

[0010] Preferably, the specific atmosphere is a nitrogen atmosphere, wherein the nitrogen concentration is 78%-99%.

[0011] Preferably, the mixing reaction time is 2-24h.

[0012] Preferably, the mixed reaction temperature is 50-300°C.

[0013] Preferably, the mixing reaction mode is stirring or ball milling.

[0014] Preferably, the stirring or ball milling method is set at a rotation speed of 30-150 rpm.

[0015] Preferably, the mixing method adopts one of a ball mill mixer, a drum mixer, a high-speed mixer, a cone mixer, a ribbon mixer and a plowshare mixer.

[0016] A positive electrode lithium replenishing material is prepared by the above-mentioned preparation method of the positive electrode lithium replenishing agent material.

[0017] Preferably, during the homogenization process of the positive electrode of the lithium ion battery, the positive electrode lithium supplement material is directly added into the lithium ion battery.

[0018] Preferably, the mass of the positive electrode lithium supplement material is 0.05wt%-0.5wt% of the mass of the positive electrode sheet active material of the lithium ion battery.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects:

[0020] The present invention provides a positive electrode lithium replenisher material. Under a specific environment, Li2NiO2 is mixed and reacted in a specific atmosphere to obtain a Li2NiO2 positive electrode lithium replenisher material with a core-shell structure, wherein the core is Li2NiO2 and the shell is the reaction product Li3N. The positive electrode lithium replenisher can generate Li3N on the surface in a specific environment. Li3N isolates the reaction between moisture and the inner layer of the lithium replenisher, solves the problem that the positive electrode lithium replenisher material is sensitive to moisture, improves the environmental stability of the material, avoids the occurrence of gelation after the positive electrode lithium replenisher material is added to the positive electrode slurry, and thus improves the safety performance of the lithium ion battery. In addition, the application of the positive electrode lithium replenisher material prepared by the present invention in lithium ion batteries effectively improves the service life and safety performance of lithium ion batteries.

[0021] Furthermore, the reaction product Li2NiO2 prepared by the present invention can also contribute to the capacity, and at the same time can improve the safety performance, coulombic efficiency and capacity of the battery.

[0022] Furthermore, the lithium nitride of the present invention has a high theoretical specific capacity, and adding a small amount thereof can improve the first-cycle coulombic efficiency of the battery.

[0023] Furthermore, the preparation process of the present invention is simple, the production cost is low and it is more environmentally friendly. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0025] A method for preparing a positive electrode lithium supplement material, comprising:

[0026] The positive electrode lithium replenisher Li2NiO2 is mixed with nitrogen in a specific atmosphere to obtain a positive electrode lithium replenishing material. The specific atmosphere is a nitrogen atmosphere, wherein the nitrogen concentration is 78%-99%, the mixing reaction time is 2-24h, the mixing reaction temperature is 50-300°C, the mixing reaction method is stirring or ball milling, the stirring or ball milling method is set to a speed of 30-150rpm, and the mixing method uses one of a ball mill mixer, a drum mixer, a high-speed mixer, a cone mixer, a screw belt mixer and a plowshare mixer.

[0027] A positive electrode lithium replenishing material is used in a lithium ion battery. During the positive electrode homogenization process of the lithium ion battery, the positive electrode lithium replenishing material is directly added to the lithium ion battery. The mass of the positive electrode lithium replenishing material is 0.05wt%-0.5wt% of the mass of the active material of the positive electrode sheet of the lithium ion battery.

[0028] Embodiment 1

[0029] A positive electrode lithium replenishing material comprises a positive electrode lithium replenishing material and a Li3N layer coated on the surface of the positive electrode lithium replenishing material.

[0030] The positive electrode lithium supplement material comprises the following steps:

[0031] In an atmosphere with a nitrogen concentration of 85%, nitrogen is continuously introduced, and the positive electrode lithium replenisher Li2NiO2 is stirred and mixed in a ball mill mixer at a temperature of 150°C for 10 hours, and the stirring speed is 80rpm to obtain the positive electrode lithium replenishing material; the prepared positive electrode lithium replenishing material is applied to a lithium ion battery, and the above-mentioned positive electrode lithium replenishing material is directly added during the positive electrode homogenization process to prepare a lithium ion battery, wherein the mass of the positive electrode lithium replenishing material is 0.2wt% of the mass of the active material of the lithium ion battery positive electrode sheet.

[0032] Embodiment 2

[0033] A positive electrode lithium replenishing material comprises a positive electrode lithium replenishing material and a Li3N layer coated on the surface of the positive electrode lithium replenishing material.

[0034] The positive electrode lithium supplement material comprises the following steps:

[0035] In an atmosphere with a nitrogen concentration of 88%, nitrogen is continuously introduced, and the positive electrode lithium replenisher Li2NiO2 is stirred and mixed in a drum mixer at a temperature of 150°C for 11 hours, and the stirring speed is 100rpm to obtain the positive electrode lithium replenishing material; the prepared positive electrode lithium replenishing material is applied to a lithium ion battery, and the above-mentioned positive electrode lithium replenishing material is directly added during the positive electrode homogenization process to prepare a lithium ion battery, wherein the mass of the positive electrode lithium replenishing material is 0.2wt% of the mass of the active material of the lithium ion battery positive electrode sheet.

[0036] Embodiment 3

[0037] A positive electrode lithium replenishing material comprises a positive electrode lithium replenishing material and a Li3N layer coated on the surface of the positive electrode lithium replenishing material.

[0038] The positive electrode lithium supplement material comprises the following steps:

[0039] In an atmosphere with a nitrogen concentration of 90%, nitrogen is continuously introduced, and the positive electrode lithium replenisher Li2NiO2 is stirred and mixed in a drum mixer at a temperature of 200°C for 13 hours, and the stirring speed is 100rpm to obtain the positive electrode lithium replenishing material; the prepared positive electrode lithium replenishing material is applied to a lithium ion battery, and the above-mentioned positive electrode lithium replenishing material is directly added during the positive electrode homogenization process to prepare a lithium ion battery, wherein the mass of the positive electrode lithium replenishing material is 0.2wt% of the mass of the active material of the lithium ion battery positive electrode sheet.

[0040] Embodiment 3

[0041] A positive electrode lithium replenishing material comprises a positive electrode lithium replenishing material and a Li3N layer coated on the surface of the positive electrode lithium replenishing material.

[0042] The positive electrode lithium supplement material comprises the following steps:

[0043] In an atmosphere with a nitrogen concentration of 90%, nitrogen is continuously introduced, and the positive electrode lithium replenisher Li2NiO2 is stirred and mixed in a drum mixer at a temperature of 200°C for 13 hours, and the stirring speed is 100rpm to obtain the positive electrode lithium replenishing material; the prepared positive electrode lithium replenishing material is applied to a lithium ion battery, and the above-mentioned positive electrode lithium replenishing material is directly added during the positive electrode homogenization process to prepare a lithium ion battery, wherein the mass of the positive electrode lithium replenishing material is 0.2wt% of the mass of the active material of the lithium ion battery positive electrode sheet.

[0044] Embodiment 3

[0045] A positive electrode lithium replenishing material comprises a positive electrode lithium replenishing material and a Li3N layer coated on the surface of the positive electrode lithium replenishing material.

[0046] The positive electrode lithium supplement material comprises the following steps:

[0047] In an atmosphere with a nitrogen concentration of 90%, nitrogen is continuously introduced, and the positive electrode lithium replenisher Li2NiO2 is stirred and mixed in a drum mixer at a temperature of 200°C for 13 hours, and the stirring speed is 100rpm to obtain the positive electrode lithium replenishing material; the prepared positive electrode lithium replenishing material is applied to a lithium ion battery, and the above-mentioned positive electrode lithium replenishing material is directly added during the positive electrode homogenization process to prepare a lithium ion battery, wherein the mass of the positive electrode lithium replenishing material is 0.2wt% of the mass of the active material of the lithium ion battery positive electrode sheet.

[0048] Embodiment 4

[0049] A positive electrode lithium replenishing material comprises a positive electrode lithium replenishing material and a Li3N layer coated on the surface of the positive electrode lithium replenishing material.

[0050] The positive electrode lithium supplement material comprises the following steps:

[0051] In an atmosphere with a nitrogen concentration of 78%, nitrogen is continuously introduced, and the positive electrode lithium replenisher Li2NiO2 is stirred and mixed in a high-speed mixer at a temperature of 50°C for 2 hours, and the stirring speed is 30rpm to obtain the positive electrode lithium replenishing material; the prepared positive electrode lithium replenishing material is applied to a lithium ion battery, and the above-mentioned positive electrode lithium replenishing material is directly added during the positive electrode homogenization process to prepare a lithium ion battery, wherein the mass of the positive electrode lithium replenishing material is 0.05wt% of the mass of the active material of the lithium ion battery positive electrode sheet.

[0052] Embodiment 5

[0053] A positive electrode lithium replenishing material comprises a positive electrode lithium replenishing material and a Li3N layer coated on the surface of the positive electrode lithium replenishing material.

[0054] The positive electrode lithium supplement material comprises the following steps:

[0055] In an atmosphere with a nitrogen concentration of 99%, nitrogen is continuously introduced, and the positive electrode lithium replenisher Li2NiO2 is stirred and mixed in a drum mixer at a temperature of 300°C for 24 hours, and the stirring speed is 150rpm to obtain the positive electrode lithium replenishing material; the prepared positive electrode lithium replenishing material is applied to a lithium ion battery, and the above-mentioned positive electrode lithium replenishing material is directly added during the positive electrode homogenization process to prepare a lithium ion battery, wherein the mass of the positive electrode lithium replenishing material is 0.5wt% of the mass of the active material of the lithium ion battery positive electrode sheet.

[0056] Embodiment 6

[0057] A positive electrode lithium replenishing material comprises a positive electrode lithium replenishing material and a Li3N layer coated on the surface of the positive electrode lithium replenishing material.

[0058] The positive electrode lithium supplement material comprises the following steps:

[0059] In an atmosphere with a nitrogen concentration of 80%, nitrogen is continuously introduced, and the positive electrode lithium replenisher Li2NiO2 is stirred and mixed in a plowshare mixer at a temperature of 80°C for 6 hours, and the stirring speed is 50rpm to obtain the positive electrode lithium replenishing material; the prepared positive electrode lithium replenishing material is applied to a lithium ion battery, and the above-mentioned positive electrode lithium replenishing material is directly added during the positive electrode homogenization process to prepare a lithium ion battery, wherein the mass of the positive electrode lithium replenishing material is 0.1wt% of the mass of the active material of the lithium ion battery positive electrode sheet.

[0060] Embodiment 7

[0061] A positive electrode lithium replenishing material comprises a positive electrode lithium replenishing material and a Li3N layer coated on the surface of the positive electrode lithium replenishing material.

[0062] The positive electrode lithium supplement material comprises the following steps:

[0063] In an atmosphere with a nitrogen concentration of 95%, nitrogen is continuously introduced, and the positive electrode lithium replenisher Li2NiO2 is stirred and mixed in a ribbon mixer at a temperature of 260°C for 14 hours, and the stirring speed is 90rpm to obtain the positive electrode lithium replenishing material; the prepared positive electrode lithium replenishing material is applied to a lithium ion battery, and the above-mentioned positive electrode lithium replenishing material is directly added during the positive electrode homogenization process to prepare a lithium ion battery, wherein the mass of the positive electrode lithium replenishing material is 0.35wt% of the mass of the active material of the lithium ion battery positive electrode sheet.

[0064] Embodiment 8

[0065] A positive electrode lithium replenishing material comprises a positive electrode lithium replenishing material and a Li3N layer coated on the surface of the positive electrode lithium replenishing material.

[0066] The positive electrode lithium supplement material comprises the following steps:

[0067] In an atmosphere with a nitrogen concentration of 92%, nitrogen is continuously introduced, and the positive electrode lithium replenisher Li2NiO2 is stirred and mixed in a conical mixer at a temperature of 160°C for 18 hours, and the stirring speed is 120rpm to obtain the positive electrode lithium replenishing material; the prepared positive electrode lithium replenishing material is applied to a lithium ion battery, and the above-mentioned positive electrode lithium replenishing material is directly added during the positive electrode homogenization process to prepare a lithium ion battery, wherein the mass of the positive electrode lithium replenishing material is 0.42wt% of the mass of the active material of the lithium ion battery positive electrode sheet.

[0068] Comparative Example 1

[0069] The positive electrode lithium replenisher Li2NiO2 is used directly as the positive electrode lithium replenisher without any treatment.

[0070] NCM811 was used as the positive electrode active material, and N-methylpyrrolidone was added to conductive carbon black, polyvinylidene fluoride, and positive electrode lithium supplement in a mass ratio of 95:3:2:0.2 to prepare a slurry. Then, 2025 type button battery production tests were carried out respectively, and rate charge and discharge tests were carried out in the voltage range of 3.0V to 4.3V.

[0071] Table 1 shows the electrochemical properties of the samples of the embodiment and the comparative example.

[0072]

[0073]

[0074] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention is described in detail with reference to the above-described embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the above-described embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for preparing a positive electrode lithium supplement material, It is characterized in that include, In a specific atmosphere, the positive electrode lithium supplement Li 2 NiO 2 Mixing and reacting with nitrogen to obtain positive electrode lithium supplement material; The specific atmosphere environment is a nitrogen atmosphere, wherein the nitrogen concentration is 78%-99%; The mixed reaction temperature is 50-300°C; The positive electrode lithium supplement material is a core-shell structure, and its core is Li 2 NiO 2 , the shell is the reaction product Li 3 N.

2. A method for preparing a positive electrode lithium supplement material according to claim 1, It is characterized in that The mixing reaction time is 2-24h.

3. A method for preparing a positive electrode lithium supplement material according to claim 1, It is characterized in that The mixing reaction mode is stirring or ball milling.

4. A method for preparing a positive electrode lithium supplement material according to claim 3, It is characterized in that The stirring or ball milling method is set to have a rotation speed of 30-150 rpm.

5. A method for preparing a positive electrode lithium supplement material according to claim 1, It is characterized in that The mixing method adopts one of a ball mill mixer, a drum mixer, a high-speed mixer, a cone mixer, a ribbon mixer and a plowshare mixer.

6. A positive electrode lithium supplement material, It is characterized in that The method is based on the preparation method of the positive electrode lithium supplement material according to any one of claims 1 to 5.

7. Use of the positive electrode lithium supplement material according to claim 6 in a lithium ion battery, It is characterized in that During the homogenization process of the positive electrode of the lithium-ion battery, the positive electrode lithium supplement material is directly added into the lithium-ion battery.

8. Application of a positive electrode lithium supplement material according to claim 7 in a lithium ion battery, It is characterized in that The mass of the positive electrode lithium supplement material is 0.05wt%-0.5wt% of the mass of the positive electrode sheet active material of the lithium ion battery.

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