Preparation method and application of polymer coated silicon-based composite material

Abstract

The invention discloses a preparation method and application of a polymer coated silicon-based composite material. Belongs to the technical field of secondary ion batteries and comprises the following preparation steps: firstly, mixing a polymer precursor material with a silicon-based material, and heating to a reaction temperature in an inert atmosphere; then, molecules of the precursor material are uniformly attached to the surface of the silicon-based material, dehalogenation polymerization reaction is further carried out, a polymer coating layer is formed, and a polymer-coated silicon-based composite material is obtained; and finally, mixing the polymer-coated silicon-based composite material, a conductive agent and a binder, and coating a current collector with the mixture to prepare the battery electrode plate. The polymer coated silicon-based composite material obtained by the invention has excellent cycle performance and rate capability, especially in a lithium ion battery; the preparation method is simple in process and suitable for large-scale production, and has great industrial application potential.

Description

Technical Field

[0001] The invention belongs to the technical field of secondary ion battery materials and relates to a preparation method of a polymer-coated silicon-based composite material and application thereof. Background Art

[0002] With the rapid development of electric vehicles and portable electronic devices, secondary ion batteries with high energy density and long cycle life have become a research focus, especially lithium-ion batteries. Traditional lithium-ion batteries use graphite as the negative electrode material, but their theoretical specific capacity is low (372mAh / g), which makes it difficult to meet the growing demand for high-performance energy storage in the consumer market.

[0003] Silicon (Si)-based anode materials are considered one of the most promising next-generation anode materials due to their ultra-high theoretical specific capacity (for example, elemental Si has 4200mAh / g, more than 10 times that of graphite) and suitable operating voltage (<0.5V vs. Li+ / Li). However, silicon-based anodes face significant challenges during use, among which the problem of elemental Si is the most significant. During the charge and discharge process, the volume of elemental Si changes by as much as 300% due to the insertion and extraction of lithium ions. The huge volume change can lead to electrode structure rupture, loss of active materials, and ultimately rapid decay of battery capacity. At the same time, the drastic volume change can cause repeated rupture and regeneration of the solid electrolyte interface (SEI) film, continuously consuming electrolyte and increasing interfacial impedance, thereby reducing battery life. In addition, the low conductivity of Si itself limits the charge transfer efficiency.

[0004] Therefore, developing a silicon-based negative electrode material that combines high capacity, long life and low cost is a key technical problem that needs to be urgently solved in the field of lithium-ion batteries. Summary of the Invention

[0005] Purpose of the invention: The purpose of the present invention is to provide a method for preparing a polymer-coated silicon-based composite material with high capacity, long life and low cost. Another purpose of the present invention is to provide an application of the polymer-coated silicon-based composite material in battery negative electrode materials.

[0006] Technical solution: The method for preparing a polymer-coated silicon-based composite material according to the present invention comprises the following steps:

[0007] (1) fully mixing the polymer precursor material and the silicon-based material in proportion to obtain a uniform mixture;

[0008] (2) placing the homogeneous mixture under an inert gas atmosphere and heating it to the dehalogenation polymerization reaction temperature of the precursor material;

[0009] (3) maintaining the reaction temperature for a period of time until sufficient polymerization occurs, forming a uniformly coated polymer layer on the surface of the silicon-based material, and obtaining a polymer-coated silicon-based composite material;

[0010] (4) The polymer-coated silicon-based composite material is mixed with a conductive agent and a binder in proportion and then coated on a current collector to prepare a battery electrode sheet.

[0011] Furthermore, the polymer precursor material in step (1) is an organic molecule having a benzene ring structure and two or more halogenated aromatic groups, which is mainly divided into two categories: halogenated six-membered aromatic rings and halogenated thiophenes, including but not limited to one or more of the following structures:

[0012]

[0013] Wherein, X represents H, F, CI, Br or I;

[0014] Y represents CH or N.

[0015] Furthermore, the silicon-based material in step (1) is one or more silicon-based negative electrode materials of elemental silicon, silicon oxide or silicon-lithium alloy, such as nano silicon (100nm), micro silicon (5μm), silicon oxide (500nm), etc.

[0016] Furthermore, in step (1), the mass ratio of the polymer precursor material to the silicon-based material is (0.01-0.5):1.

[0017] Furthermore, the mixing method in step (1) includes stirring and mixing dry materials or solvent-assisted mixing followed by evaporation to remove the solvent, wherein the auxiliary solvent is one or more of water, ethanol, and acetonitrile.

[0018] Furthermore, in step (2), the inert gas is one or more of nitrogen, argon, and helium; the temperature of the dehalogenation polymerization reaction is 300-700° C., and the reaction time is 0.5-5 h.

[0019] Furthermore, the time for maintaining the reaction temperature in step (3) is 0.5 to 5 hours.

[0020] Furthermore, in step (4), the mass ratio of the polymer-coated silicon-based composite material, the conductive agent, and the binder is 50-95:2.5-25:2.5-25.

[0021] Furthermore, in step (4), the conductive agent is one or more of Sup-p and Ketjen black; the binder is one or more of sodium alginate (CHONa), polytetrafluoroethylene (PTFE), and polyvinylidene fluoride (PVDF); and the current collector is one or more of copper foil and carbon paper.

[0022] Furthermore, a polymer-coated silicon-based composite material is prepared by the above preparation method.

[0023] Furthermore, the prepared polymer-coated silicon-based composite material is used as a negative electrode material for batteries, especially in lithium-ion batteries.

[0024] Features of the present invention: The present invention first adopts dry material mixing or solution-assisted mixing to fully mix the polymer precursor material and the silicon-based material, and makes the precursor material molecules evenly adhere to the surface of the silicon-based material by high-temperature evaporation, adsorption, and melting; the precursor material molecules undergo dehalogenation polymerization at the reaction temperature to form a uniform polymer coating layer on the surface of the silicon-based material, without the need for other treatment, to obtain a polymer-coated silicon-based composite material; finally, the polymer-coated silicon-based composite material is prepared into a battery electrode sheet as the negative electrode of a lithium-ion battery.

[0025] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: 1. The preparation method of the polymer-coated silicon-based composite material in the present invention does not require a large amount of solution, is simple to operate, and has simple equipment requirements; 2. The polymer precursor material designed in the present invention has a suitable sublimation and polymerization reaction temperature, and can be spontaneously and uniformly adsorbed on the surface of the silicon-based material, thereby facilitating the formation of a uniform polymer coating layer with controllable thickness; 3. The precursor material has a specific molecular structure and dehalogenation polymerization site, and the generated polymer coating layer has a specific pore structure, which is convenient for the desolvation and rapid transmission of ions; 4. The polymer coating layer in the present invention has greater mechanical strength, which can inhibit the volume expansion of the silicon-based material when storing ions, prevent the breakage of the active material and the pulverization of the electrode, and effectively extend the cycle life of the silicon-based negative electrode; 5. The preparation method of the polymer-coated silicon-based composite material in the present invention does not require a large amount of solution, is safe and pollution-free, simple to operate, low cost, and suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 In Example 1 of the present invention (Si 100nm @M1) Scanning electron microscopy (SEM) images of the prepared samples;

[0027] Figure 2 In Example 1 of the present invention (Si 100nm @M1) X-ray diffraction pattern (XRD) of the prepared sample;

[0028] Figure 3 In Example 1 of the present invention (Si 100nm @M1) Raman spectrum of the prepared sample;

[0029] Figure 41 is a graph showing the cycle performance of samples of Example 1, Example 2, Example 3, Example 6 and Comparative Example 1 of the present invention as lithium-ion battery electrode sheets;

[0030] Figure 5 Graph showing the cycle performance of samples of Example 4, Example 5 and Comparative Example 2 of the present invention as lithium-ion battery electrode sheets;

[0031] Figure 6 This is a graph showing the cycle performance of samples of Example 7, Example 8 and Comparative Example 3 of the present invention as lithium-ion battery electrode sheets. DETAILED DESCRIPTION

[0032] The specific technical solutions of the present invention are further described in detail below with reference to specific examples.

[0033] In the following embodiments of the present invention, the energy storage performance test steps of the polymer-coated silicon-based composite material as the negative electrode of a lithium-ion battery are as follows: the prepared polymer-coated silicon-based composite material electrode sheet is used as the working electrode, the metal lithium sheet is used as the counter electrode, the electrolyte composition is "1M LiPF6 in EC:DEC=3:7wt% with 10% FEC", and then a charge and discharge test is performed between 0.01-1.00V, and the test temperature is room temperature.

[0034] Example 1

[0035] The polymer precursor material M1 and nano-silicon (100 nm) were weighed in a mass ratio of 0.01:1, and the two powders were poured into a blender and stirred and mixed thoroughly to obtain a uniform mixture; the mixture was transferred to a high-temperature reactor filled with inert gas, and the temperature was increased to 520°C at a rate of 15°C / min and maintained at this temperature for 2 hours to obtain a polymer-coated silicon-based composite material (Si 100nm @M1); Si 100nm The @M1 composite material was fully mixed with Sup-p and CHONa in a mass ratio of 8:1:1 to prepare an electrode slurry, which was then coated on copper foil to obtain a battery electrode sheet, and the performance of the electrode sheet was tested.

[0036] Example 2

[0037] The polymer precursor material M2 and nano-silicon (100 nm) were weighed in a mass ratio of 0.1:1, and the M2 powder was poured into ethanol and fully dispersed to form a dispersion. Then, the nano-silicon was added, stirred and mixed, and then dried to remove the ethanol to obtain a uniform mixture. The mixture was transferred to a high-temperature reactor filled with inert gas, heated to 540°C at a rate of 15°C / min, and maintained at this temperature for 1 hour to obtain a polymer-coated silicon-based composite material (Si 100nm @M2); Si 100nmThe @M2 composite material was fully mixed with Sup-p and CHONa in a mass ratio of 90:5:5, and the electrode slurry was coated on copper foil to obtain a battery electrode sheet, and the performance of the electrode sheet was tested.

[0038] Example 3

[0039] The polymer precursor material M4 and nano-silicon (100 nm) were weighed in a mass ratio of 0.2:1, and the two powders were poured into a blender and stirred and mixed thoroughly to obtain a uniform mixture; the mixture was transferred to a high-temperature reactor filled with inert gas, and the temperature was increased to 450°C at a rate of 15°C / min and maintained at this temperature for 4 hours to obtain a polymer-coated silicon-based composite material (Si 100nm @M4); Si 100nm The @M4 composite material was fully mixed with Ketjen Black and CHONa in a mass ratio of 80:1:1 to prepare an electrode slurry, which was then coated on copper foil to obtain a battery electrode sheet, and the performance of the electrode sheet was tested.

[0040] Example 4

[0041] The polymer precursor material M6 and micron silicon (5 μm) were weighed in a mass ratio of 0.1:1, and the two powders were poured into a blender and stirred and mixed thoroughly to obtain a uniform mixture; the mixture was transferred to a high-temperature reactor filled with inert gas, and the temperature was increased to 600 ° C at a rate of 20 ° C / min and maintained at this temperature for 3 hours to obtain a polymer-coated silicon-based composite material (Si 5μm @M6); Si 5μm The @M6 composite material was fully mixed with Sup-p and CHONa in a mass ratio of 90:5:5 to prepare an electrode slurry, which was then coated on carbon paper to obtain a battery electrode sheet, and the performance of the electrode sheet was tested.

[0042] Example 5

[0043] The polymer precursor material M8 and micron silicon (5 μm) were weighed in a mass ratio of 0.4:1, and the two powders were poured into a blender and stirred and mixed thoroughly to obtain a uniform mixture; the mixture was transferred to a high-temperature reactor filled with inert gas, and the temperature was increased to 650 ° C at a rate of 20 ° C / min and maintained at this temperature for 4 hours to obtain a polymer-coated silicon-based composite material (Si 5μm @M8); Si 5μm The @M8 composite material was fully mixed with Ketjen Black and CHONa in a mass ratio of 60:25:15 to prepare an electrode slurry, which was then coated on carbon paper to obtain a battery electrode sheet, and the performance of the electrode sheet was tested.

[0044] Example 6

[0045] The polymer precursor material M9 and nano-silicon (100 nm) were weighed in a mass ratio of 0.2:1, and the two powders were poured into a blender and stirred and mixed thoroughly to obtain a uniform mixture; the mixture was transferred to a high-temperature reactor filled with inert gas, and the temperature was increased to 400°C at a rate of 10°C / min and maintained at this temperature for 3 hours to obtain a polymer-coated silicon-based composite material (Si 100nm @M9); Si 100nm The @M9 composite material was fully mixed with Sup-p and CHONa in a mass ratio of 80:10:10 to prepare an electrode slurry, which was then coated on copper foil to obtain a battery electrode sheet, and the performance of the electrode sheet was tested.

[0046] Example 7

[0047] The polymer precursor material M3 and silicon oxide (500 nm) were weighed in a mass ratio of 0.1:1. The M3 powder was poured into ethanol and fully dispersed to form a dispersion. Then, silicon oxide was added and stirred thoroughly, and then dried to remove the ethanol to obtain a uniform mixture. The mixture was transferred to a high-temperature reactor filled with inert gas, heated to 500°C at a rate of 20°C / min, and maintained at this temperature for 2 hours to obtain a polymer-coated silicon-based composite material (SiO2 500nm @M3); SiO2 500nm The @M3 composite material was fully mixed with Sup-p and CHONa in a mass ratio of 70:20:10 to prepare an electrode slurry, which was then coated on copper foil to obtain a battery electrode sheet, and the performance of the electrode sheet was tested.

[0048] Example 8

[0049] The polymer precursor material M7 and silicon oxide (500 nm) were weighed in a mass ratio of 0.2:1, and the two powders were poured into a blender and stirred and mixed thoroughly to obtain a uniform mixture; the mixture was transferred to a high-temperature reactor filled with inert gas, and the temperature was increased to 450°C at a rate of 15°C / min and maintained at this temperature for 4 hours to obtain a polymer-coated silicon-based composite material (SiO2 500nm @M7); SiO2 500nm The @M7 composite material was fully mixed with Ketjen Black and CHONa in a mass ratio of 60:25:15 to prepare an electrode slurry, which was then coated on carbon paper to obtain a battery electrode sheet, and the performance of the electrode sheet was tested.

[0050] Comparative Example 1

[0051] Nano-silicon (100 nm) was fully mixed with Sup-p and CHONa in a mass ratio of 8:1:1 to prepare an electrode slurry, which was then coated on copper foil to obtain a battery electrode sheet, and the performance of the electrode sheet was tested.

[0052] Comparative Example 2

[0053] Micron silicon (5 μm) was fully mixed with Sup-p and CHONa in a mass ratio of 90:5:5 to prepare an electrode slurry, which was then coated on carbon paper to obtain a battery electrode sheet, and the performance of the electrode sheet was tested.

[0054] Comparative Example 3

[0055] Silicon oxide (500 nm) was fully mixed with Sup-p and CHONa in a mass ratio of 70:20:10 to prepare an electrode slurry, which was then coated on copper foil to obtain a battery electrode sheet, and the performance of the electrode sheet was tested.

[0056] In summary, the various polymer-coated silicon-based composite materials prepared by the present invention have a safe and pollution-free manufacturing process, simple operation, low cost, and are suitable for large-scale production; the polymer coating layer obtained by dehalogenation polymerization in the present invention inhibits the volume expansion of the silicon-based material when storing lithium ions, effectively preventing the breakage of the active material and the pulverization of the electrode; the various polymer-coated silicon-based composite materials obtained by the present invention effectively improve the cycle performance of the silicon-based negative electrode of the lithium-ion battery compared with the unimproved silicon-based material.

Claims

1. A method for preparing a polymer-coated silicon-based composite material, characterized in that: The steps include: (1) mixing the polymer precursor material and the silicon-based material in proportion to obtain a uniform mixture; (2) placing the homogeneous mixture under an inert gas atmosphere and heating it to the dehalogenation polymerization reaction temperature of the precursor material; (3) maintaining the reaction temperature until polymerization occurs, forming a uniformly coated polymer layer on the surface of the silicon-based material, and obtaining a polymer-coated silicon-based composite material; (4) The polymer-coated silicon-based composite material is mixed with a conductive agent and a binder in proportion and then coated on a current collector to prepare a battery electrode sheet.

2. The method for preparing a polymer-coated silicon-based composite material according to claim 1, characterized in that: The polymer precursor material in step (1) is an organic molecule having a benzene ring structure and two or more halogenated aromatic groups, which is divided into two categories: a halogenated six-membered aromatic ring and a halogenated thiophene, and includes but is not limited to one or more of the following structures: Wherein, X represents H, F, CI, Br or I; Y represents CH or N.

3. The method for preparing a polymer-coated silicon-based composite material according to claim 1, characterized in that: The silicon-based material in step (1) is one or more silicon-based negative electrode materials selected from elemental silicon, silicon oxide, or silicon-lithium alloy.

4. The method for preparing a polymer-coated silicon-based composite material according to claim 1, characterized in that: In the step (1), the mass ratio of the polymer precursor material to the silicon-based material is (0.01-0.5):

1.

5. The method for preparing a polymer-coated silicon-based composite material according to claim 1, characterized in that: The mixing method in step (1) includes stirring and mixing dry materials or solvent-assisted mixing followed by evaporation to remove the solvent, wherein the auxiliary solvent is one or more of water, ethanol, and acetonitrile.

6. The method for preparing a polymer-coated silicon-based composite material according to claim 1, characterized in that: In step (2), the inert gas is one or more of nitrogen, argon, and helium; the temperature of the dehalogenation polymerization reaction is 300-700° C., and the reaction time is 0.5-5 h.

7. The method for preparing a polymer-coated silicon-based composite material according to claim 1, characterized in that: The time for maintaining the reaction temperature in step (3) is: 0.5 to 5 hours.

8. The method for preparing a polymer-coated silicon-based composite material according to claim 1, characterized in that: In the step (4), the mass ratio of the polymer-coated silicon-based composite material, the conductive agent, and the binder is 50-95:2.5-25:2.5-25.

9. The method for preparing a polymer-coated silicon-based composite material according to claim 1, characterized in that: In the step (4), the conductive agent is one or more of Sup-p and Ketjen black; the binder is one or more of sodium alginate, polytetrafluoroethylene, and polyvinylidene fluoride; and the current collector is one or more of copper foil and carbon paper.

10. Use of the polymer-coated silicon-based composite material prepared by the preparation method according to any one of claims 1 to 9 as a negative electrode material for a battery.

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