Negative electrode of lithium-ion battery, preparation method thereof, lithium-ion battery and vehicle

Abstract

The present invention provides a negative electrode of a lithium-ion battery, a preparation method thereof, a lithium-ion battery, and a vehicle. Among them, the preparation method of the negative electrode of the lithium-ion battery includes: adding tetrabutyl titanate and n-octadecyl phosphate into N,N-dimethyltrifluoroacetamide to obtain a negative electrode treatment solution; soaking the negative electrode of the lithium-ion battery in the negative electrode treatment solution, and forming a protective layer including lithium titanate, lithium phosphate, and organoalkyl lithium on the surface of the negative electrode of the lithium-ion battery through molecular self-assembly. By means of molecular self-assembly, a protective layer including lithium titanate, lithium phosphate, and organoalkyl lithium is attached to the surface of the metallic lithium negative electrode, thereby effectively avoiding the direct contact of the metallic lithium negative electrode with oxygen and moisture in the air, and effectively improving the stability of the lithium-ion battery using metallic lithium as the negative electrode. At the same time, the protective layer including lithium titanate, lithium phosphate, and organoalkyl lithium can be prepared by a relatively simple preparation method, reducing the production cost and the production threshold.

Description

Technical Field

[0001] The present invention relates to the field of lithium - ion batteries, and particularly to a negative electrode of a lithium - ion battery, a preparation method of a negative electrode of a lithium - ion battery, a lithium - ion battery, and a vehicle. Background Art

[0002] Generally speaking, due to the high theoretical specific capacity, low potential and light mass of metallic lithium, it can better improve the energy density of lithium - ion batteries and is considered to be a potential negative electrode material for next - generation batteries. However, on the one hand, metallic lithium has problems of interface stability and dendrite growth, and on the other hand, it is unstable in air, resulting in difficulties in the production and use of metallic lithium in lithium - ion batteries. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a negative electrode of a lithium - ion battery, a preparation method of a negative electrode of a lithium - ion battery, a lithium - ion battery, and a vehicle, so as to improve the stability of the negative electrode of the lithium - ion battery.

[0004] To solve the above problems, the present invention discloses a preparation method of a negative electrode of a lithium - ion battery, including:

[0005] Adding tetrabutyl titanate and octadecyl phosphate into N,N - dimethyltrifluoroacetamide to obtain a negative - electrode treatment solution;

[0006] Soaking the negative electrode of the lithium - ion battery in the negative - electrode treatment solution, and forming a protective layer including lithium titanate, lithium phosphate and organo - alkyl lithium on the surface of the negative electrode of the lithium - ion battery through molecular self - assembly.

[0007] Optionally, in the negative - electrode treatment solution, the mass percentage concentration of tetrabutyl titanate is 0.05 - 2 wt%.

[0008] Optionally, in the negative - electrode treatment solution, the mass percentage concentration of octadecyl phosphate is 0.05 - 2 wt%.

[0009] Optionally, the soaking time of the negative electrode of the lithium - ion battery in the negative - electrode treatment solution is 3 - 10 minutes.

[0010] The present invention also provides a negative electrode of a lithium - ion battery. The base material of the negative electrode of the lithium - ion battery is lithium metal, and a protective layer including lithium titanate, lithium phosphate and organo - alkyl lithium is coated on the surface of the base material.

[0011] Optionally, the protective layer is obtained by performing a molecular self - assembly reaction on the lithium metal negative electrode and a negative - electrode treatment solution containing tetrabutyl titanate and octadecyl phosphate.

[0012] Optionally, the negative electrode of the lithium-ion battery is formed by at least one of lithium powder, lithium sheet, and lithium foil.

[0013] Optionally, the protective layer is used to block the reaction of moisture and / or oxygen in the environment with the negative electrode of the lithium-ion battery.

[0014] The present invention also provides a lithium-ion battery, which includes a negative electrode of a lithium-ion battery prepared by the method for preparing a negative electrode of a lithium-ion battery according to the present invention, or includes a negative electrode of a lithium-ion battery according to the present invention.

[0015] The present invention also provides a vehicle, which includes a lithium-ion battery according to the present invention.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] In the present invention, a protective layer containing lithium titanate, lithium phosphate, and organic alkyl lithium is attached to the surface of the metallic lithium negative electrode by means of molecular self-assembly, so that the metallic lithium negative electrode can be effectively prevented from directly contacting with oxygen and moisture in the air, and the stability of the lithium-ion battery with the metallic lithium as the negative electrode is effectively improved. At the same time, the protective layer containing lithium titanate, lithium phosphate, and organic alkyl lithium can be prepared by a relatively simple preparation method, reducing the production cost and production threshold, and facilitating application in actual production and actual application in vehicles. Description of the Drawings

[0018] Figure 1 is a schematic diagram of a method for preparing a negative electrode of a lithium-ion battery according to an embodiment of the present invention. Detailed Embodiments

[0019] In order to make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0020] The present invention provides a method for preparing a negative electrode of a lithium-ion battery, including:

[0021] Adding tetrabutyl titanate and n-octadecyl phosphate into N,N-dimethyltrifluoroacetamide to obtain a negative electrode treatment solution;

[0022] Soaking the negative electrode of the lithium-ion battery in the negative electrode treatment solution, and forming a protective layer including lithium titanate, lithium phosphate, and organic alkyl lithium on the surface of the negative electrode of the lithium-ion battery through molecular self-assembly.

[0023] Specifically, when tetrabutyl titanate and octadecyl phosphate are dissolved in N,N-dimethyltrifluoroacetamide, if added to the negative electrode of a lithium-ion battery, at the solid-liquid interface between the negative electrode of the lithium-ion battery as a solid substrate and the negative electrode treatment liquid as a liquid phase, the tetrabutyl titanate and octadecyl phosphate in N,N-dimethyltrifluoroacetamide can undergo solute transfer and transfer to the surface of the negative electrode of the lithium-ion battery, where a low-density solid phase can form between molecules. Subsequently, tetrabutyl titanate and octadecyl phosphate can further react to generate lithium titanate, lithium phosphate, and organoalkyl lithium and self-assemble. Through the intermolecular interaction forces, lithium titanate, lithium phosphate, and organoalkyl lithium can adhere to the surface of the negative electrode of the lithium-ion battery. Their head groups can form strong chemical bonds with the negative electrode of the lithium-ion battery, while the tail groups can form an ordered structure, forming a protective layer with good coating properties, inorganic / organic hybrid, including lithium titanate, lithium phosphate, and organoalkyl lithium. Among them, the organoalkyl lithium can be a lithium compound with a long-chain organoalkyl hydrocarbon, such as lithium octadecyl and lithium octadecyloxy. The present invention does not limit this. In the presence of a protective layer containing lithium titanate, lithium phosphate, and organoalkyl lithium, the protective layer can have good hydrophobic properties, can block moisture and oxygen in the environment, and improve the stability of the negative electrode of the lithium-ion battery. At the same time, the protective layer does not block the transmission of lithium ions and electrons, ensuring that the negative electrode of the lithium-ion battery can maintain good performance.

[0024] Specifically, the negative electrode of the lithium-ion battery can be lithium metal. The negative electrode of the lithium-ion battery coated with a protective layer containing lithium titanate, lithium phosphate, and organoalkyl lithium can have good stability in dry air (dew point -40°C), and can effectively inhibit the generation of lithium dendrites and large volume deformation of metallic lithium during the cycling process, improving the cycling efficiency of metallic lithium.

[0025] In an embodiment of the present invention, in the negative electrode treatment liquid, the mass percentage concentration of tetrabutyl titanate is 0.05 - 2 wt%.

[0026] In an embodiment of the present invention, in the negative electrode treatment liquid, the mass percentage concentration of octadecyl phosphate is 0.05 - 2 wt%.

[0027] Specifically, by reasonably selecting the mass percentage concentrations of tetrabutyl titanate and octadecyl phosphate, tetrabutyl titanate and octadecyl phosphate can efficiently complete self-assembly on the surface of the negative electrode of the lithium-ion battery, forming a protective layer containing lithium titanate, lithium phosphate, and organoalkyl lithium. At the same time, the thickness of the self-assembled protective layer is appropriate and has good denseness, which can effectively improve the stability of the negative electrode of the lithium-ion battery.

[0028] In an embodiment of the present invention, the soaking duration of the negative electrode of the lithium-ion battery in the negative electrode treatment liquid is 3 - 10 minutes.

[0029] Specifically, by reasonably controlling the soaking time of the negative electrode of the lithium-ion battery in the negative electrode treatment liquid, it is possible to ensure that the protective layer including lithium titanate, lithium phosphate, and organic alkyl lithium can better cover the surface of the negative electrode of the lithium-ion battery, and at the same time, the soaking time is not too long, which can effectively improve the production efficiency of the lithium-ion battery.

[0030] The present invention also provides a negative electrode of a lithium-ion battery. The substrate of the negative electrode of the lithium-ion battery is lithium metal, and the surface of the substrate is coated with a protective layer including lithium titanate, lithium phosphate, and organic alkyl lithium.

[0031] Specifically, lithium metal can be used as the negative electrode of the lithium-ion battery. However, lithium metal is prone to the growth of lithium dendrites, resulting in poor safety. At the same time, the chemical activity of lithium metal is too high, resulting in poor stability of lithium metal in the air. These problems have seriously hindered the practical application process of using lithium metal as the negative electrode of the lithium-ion battery. In addition, lithium is extremely sensitive to moisture and oxidizing components in the air. Insulating products generated by the reaction, such as LiOH, etc., are likely to accumulate on the surface of lithium metal, reducing its electrochemical performance. More seriously, if lithium accidentally comes into contact with water, a violent hydrogen-producing and heat-producing reaction will occur, resulting in combustion and explosion. This makes the requirements for the operating processes, equipment, and environment of lithium metal in the transportation, storage, and processing processes extremely harsh.

[0032] Therefore, a protective layer including lithium titanate, lithium phosphate, and organic alkyl lithium can be coated on the surface of the lithium metal substrate. The protective layer including lithium titanate, lithium phosphate, and organic alkyl lithium can have good hydrophobic properties, which can block moisture and oxygen in the environment and improve the stability of the negative electrode of the lithium-ion battery. At the same time, the protective layer does not block the transmission of lithium ions and electrons, ensuring that the negative electrode of the lithium-ion battery can maintain good performance, so that the substrate of lithium metal can be applied to the lithium-ion battery, and the negative electrode of the lithium-ion battery with lithium metal can maintain good stability in the substrate of lithium metal and can effectively inhibit the generation of lithium dendrites and large volume deformation of lithium metal during the cycling process, improving the cycling efficiency of lithium metal.

[0033] In an embodiment of the present invention, the protective layer is obtained by performing a molecular self-assembly reaction on the lithium metal negative electrode and a negative electrode treatment liquid containing tetrabutyl titanate and n-octadecyl phosphate.

[0034] Specifically, the protective layer can be obtained by adding tetrabutyl titanate and n-octadecyl phosphate to N,N-dimethyltrifluoroacetamide to obtain a negative electrode treatment liquid; soaking the negative electrode of the lithium-ion battery in the negative electrode treatment liquid, and forming a protective layer including lithium titanate, lithium phosphate, and organic alkyl lithium on the surface of the negative electrode of the lithium-ion battery through molecular self-assembly.

[0035] Add a lithium-ion battery negative electrode to the negative electrode treatment solution. Molecular self-assembly can occur at the solid-liquid junction between the lithium-ion battery negative electrode as the solid substrate and the negative electrode treatment solution as the liquid phase. Tetrabutyl titanate and n-octadecyl phosphate in N,N-dimethyltrifluoroacetamide can adhere to the surface of the lithium-ion battery negative electrode and react to form lithium titanate, lithium phosphate, and organoalkyl lithium, while forming an ordered structure, thereby forming a protective layer with good coating properties. The protective layer can block moisture and oxygen in the environment while not blocking the transmission of lithium ions and electrons. This enables metallic lithium to be practically applied as the negative electrode in a lithium-ion battery and have good stability.

[0036] In one embodiment of the present invention, the lithium-ion battery negative electrode is formed by at least one of lithium powder, lithium sheet, and lithium foil.

[0037] Specifically, the lithium-ion battery negative electrode can be formed by metallic lithium in at least one form of lithium powder, lithium sheet, and lithium foil. Specifically, lithium powder or lithium foil can be pressed into a lithium-ion battery negative electrode, or a lithium sheet can be directly used as the lithium-ion battery negative electrode. Or lithium powder can be mixed with other materials suitable for use as a lithium-ion battery negative electrode, such as carbon, silicon-based oxides, etc., and pressed into a lithium-ion battery negative electrode. A lithium foil can also be attached to the surface of other materials suitable for use as a lithium-ion battery negative electrode, such as carbon, silicon-based oxides, etc., to form a lithium-ion battery negative electrode. The present invention does not limit this.

[0038] In one embodiment of the present invention, the protective layer is used to block the reaction of moisture and / or oxygen in the environment with the lithium-ion battery negative electrode.

[0039] Specifically, the protective layer can isolate the metallic lithium of the lithium-ion battery negative electrode from moisture and / or oxygen in the environment, preventing metallic lithium from reacting with moisture and / or oxygen during the production process or use process, thereby avoiding potential safety accidents caused by the reaction of metallic lithium with moisture and / or oxygen.

[0040] The present invention attaches a protective layer containing lithium titanate, lithium phosphate, and organoalkyl lithium to the surface of the metallic lithium negative electrode through molecular self-assembly, thereby effectively preventing the direct contact of the metallic lithium negative electrode with oxygen and moisture in the air, effectively improving the stability of the lithium-ion battery with metallic lithium as the negative electrode. At the same time, the protective layer containing lithium titanate, lithium phosphate, and organoalkyl lithium can be prepared by a relatively simple preparation method, reducing the production cost and production threshold, and facilitating application in actual production and practical application in vehicles.

[0041] The present invention also provides a lithium-ion battery, which includes the lithium-ion battery negative electrode prepared by the method for preparing a lithium-ion battery negative electrode as described in the present invention, or includes the lithium-ion battery negative electrode as described in the present invention. Among them, the specific structural form and working principle of the lithium-ion battery negative electrode have been described in detail in the foregoing embodiments, and will not be elaborated here.

[0042] Through the lithium-ion battery provided by the embodiment of the present invention, which uses metallic lithium as the lithium-ion battery negative electrode, the energy density and specific capacity of the lithium-ion battery can be effectively improved. At the same time, a protective layer containing lithium titanate, lithium phosphate and organic alkyl lithium is attached to the surface of the metallic lithium negative electrode, so that the metallic lithium negative electrode can be effectively prevented from directly contacting with oxygen and moisture in the air, effectively improving the stability of the lithium-ion battery with metallic lithium as the negative electrode. At the same time, the protective layer containing lithium titanate, lithium phosphate and organic alkyl lithium can be prepared by a relatively simple preparation method, reducing the production cost and production threshold, and facilitating application in actual production and actual application in vehicles.

[0043] The present invention also provides a vehicle, which includes the lithium-ion battery as described in the present invention. Among them, the specific structural form and working principle of the lithium-ion battery negative electrode have been described in detail in the foregoing embodiments, and will not be elaborated here.

[0044] Through the vehicle provided by the embodiment of the present invention, which uses a lithium-ion battery with metallic lithium as the negative electrode, the energy density and specific capacity of the lithium-ion battery can be effectively improved, so that the vehicle can have better endurance. At the same time, a protective layer containing tetrabutyl titanate and n-octadecyl phosphate is attached to the surface of the metallic lithium negative electrode by means of molecular self-assembly, so that the metallic lithium negative electrode can be effectively prevented from directly contacting with oxygen and moisture in the air, effectively improving the stability of the lithium-ion battery with metallic lithium as the negative electrode. At the same time, the protective layer containing tetrabutyl titanate and n-octadecyl phosphate can be prepared by a relatively simple preparation method, reducing the production cost and production threshold, and facilitating application in actual production and actual application in vehicles.

[0045] To enable those skilled in the art to better understand the present invention, the following describes the method for preparing the lithium-ion battery negative electrode of the present invention through multiple specific embodiments.

[0046] Example 1

[0047] Add tetrabutyl titanate accounting for 0.05 wt% of N,N-dimethyltrifluoroacetamide and n-octadecyl phosphate accounting for 0.05 wt% of N,N-dimethyltrifluoroacetamide to N,N-dimethyltrifluoroacetamide to obtain a negative electrode treatment solution;

[0048] Soak the lithium sheet in the negative electrode treatment solution for 10 minutes, and form a protective layer including lithium titanate, lithium phosphate, and organoalkyl lithium on the surface of the lithium sheet through molecular self-assembly to obtain the negative electrode of the lithium-ion battery.

[0049] Example 2

[0050] Add tetrabutyl titanate accounting for 2 wt% of N,N-dimethyltrifluoroacetamide and n-octadecyl phosphate accounting for 2 wt% of N,N-dimethyltrifluoroacetamide to N,N-dimethyltrifluoroacetamide to obtain the negative electrode treatment solution;

[0051] Soak the lithium sheet in the negative electrode treatment solution for 3 minutes, and form a protective layer including lithium titanate, lithium phosphate, and organoalkyl lithium on the surface of the lithium sheet through molecular self-assembly to obtain the negative electrode of the lithium-ion battery.

[0052] Example 3

[0053] Add tetrabutyl titanate accounting for 0.5 wt% of N,N-dimethyltrifluoroacetamide and n-octadecyl phosphate accounting for 0.5 wt% of N,N-dimethyltrifluoroacetamide to N,N-dimethyltrifluoroacetamide to obtain the negative electrode treatment solution;

[0054] Soak the lithium sheet in the negative electrode treatment solution for 5 minutes, and form a protective layer including lithium titanate, lithium phosphate, and organoalkyl lithium on the surface of the lithium sheet through molecular self-assembly to obtain the negative electrode of the lithium-ion battery.

[0055] Place the negative electrodes of the lithium-ion batteries prepared in Examples 1 to 3 in the air for a water splashing test, and splash water on the negative electrodes of the lithium-ion batteries. No fire or spontaneous combustion occurred in the negative electrodes of the lithium-ion batteries in Examples 1 to 3, indicating that through the preparation method of the negative electrode of the lithium-ion battery of the present invention, a protective layer including lithium titanate, lithium phosphate, and organoalkyl lithium is effectively formed on the surface of the lithium sheet, and this protective layer effectively avoids the contact of the lithium sheet with oxygen and moisture in the environment, improving the stability of the lithium sheet.

[0056] The negative electrode of the lithium-ion battery, its preparation method, the lithium-ion battery, and the vehicle provided by the present invention have been introduced in detail above. Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above examples is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A method for preparing a negative electrode of a lithium-ion battery, characterized in that, it includes: adding tetrabutyl titanate and n-octadecyl phosphate into N,N-dimethyltrifluoroacetamide to obtain a negative electrode treatment solution; immersing the negative electrode of the lithium-ion battery in the negative electrode treatment solution, and forming a protective layer including lithium titanate, lithium phosphate and organic alkyl lithium on the surface of the negative electrode of the lithium-ion battery through molecular self-assembly; the protective layer has a hydrophobic property and is used to block moisture and oxygen in the environment.

2. The method according to claim 1, characterized in that, in the negative electrode treatment solution, the mass percentage concentration of tetrabutyl titanate is 0.05-2 wt%.

3. The method according to claim 1, characterized in that, in the negative electrode treatment solution, the mass percentage concentration of n-octadecyl phosphate is 0.05-2 wt%.

4. The method according to claim 1, characterized in that, the immersion time of the negative electrode of the lithium-ion battery in the negative electrode treatment solution is 3-10 minutes.

5. A negative electrode of a lithium-ion battery, characterized in that, the negative electrode of the lithium-ion battery is prepared by the preparation method described in any one of claims 1-4, the base material of the negative electrode of the lithium-ion battery is lithium metal, and a protective layer including lithium titanate, lithium phosphate and organic alkyl lithium is coated on the surface of the base material; the protective layer has a hydrophobic property and is used to block moisture and oxygen in the environment.

6. The negative electrode of a lithium-ion battery according to claim 5, characterized in that, the protective layer is obtained by performing a molecular self-assembly reaction on the lithium metal and a negative electrode treatment solution containing tetrabutyl titanate and n-octadecyl phosphate.

7. The negative electrode of a lithium-ion battery according to claim 5, characterized in that, the negative electrode of the lithium-ion battery is formed by at least one of lithium powder and lithium flakes.

8. The negative electrode of a lithium-ion battery according to claim 5, characterized in that, the protective layer is used to block the reaction of moisture and / or oxygen in the environment with the negative electrode of the lithium-ion battery.

9. A lithium-ion battery, characterized in that, it includes a negative electrode of a lithium-ion battery prepared by the preparation method described in any one of claims 1-4, or includes a negative electrode of a lithium-ion battery described in any one of claims 5-8.

10. A vehicle, characterized in that, it includes the lithium-ion battery described in claim 9.

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