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] This invention belongs to the field of secondary ion battery materials technology, and relates to a method for preparing a polymer-coated silicon-based composite material and its application. Background Technology

[0002] With the rapid development of electric vehicles and portable electronic devices, high-energy-density, long-cycle-life secondary ion batteries have become a research focus, especially lithium-ion batteries. Traditional lithium-ion batteries use graphite as the negative electrode material, but its theoretical specific capacity is relatively low (372 mAh / g), making 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 (e.g., elemental Si has 4200 mAh / g, more than 10 times that of graphite) and suitable operating voltage (<0.5 V vs. Li+ / Li). However, silicon-based anodes face significant challenges during use, with elemental Si being the most problematic. During charge and discharge, elemental Si undergoes a volume change of up to 300% due to lithium ion insertion and extraction. This massive volume change leads to electrode structure rupture, loss of active materials, and ultimately rapid capacity decay. Simultaneously, the drastic volume change causes repeated rupture and regeneration of the solid electrolyte interphase (SEI) film, continuously consuming electrolyte and increasing interfacial impedance, thus reducing battery life. Furthermore, Si's inherent low conductivity limits charge transfer efficiency.

[0004] Therefore, developing a silicon-based anode material that balances high capacity, long lifespan, and low cost is a key technical challenge that urgently needs to be addressed in the field of lithium-ion batteries. Summary of the Invention

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

[0006] Technical solution: The present invention provides a method for preparing a polymer-coated silicon-based composite material, comprising the following steps: (1) The polymer precursor material and the silicon-based material are thoroughly mixed in proportion to obtain a homogeneous mixture; (2) Place the homogeneous mixture in an inert gas atmosphere and heat it to the dehalogenation polymerization temperature of the precursor material; (3) Maintain the reaction temperature for a period of time until the polymerization is complete, and form a uniformly coated polymer layer on the surface of the silicon-based material to obtain a polymer-coated silicon-based composite material; (4) The polymer-coated silicon-based composite material is mixed with conductive agent and binder in proportion and then coated on current collector to prepare battery electrode sheet.

[0007] Furthermore, in step (1), the polymer precursor material is an organic molecule with a benzene ring structure and two or more halogenated aromatic groups, mainly divided into two categories: halogenated six-membered aromatic rings and halogenated thiophenes, which include, but are not limited to, one or more of the following structures: ; In the formula, X represents H, F, CI, Br, or I; Y represents CH or N.

[0008] Furthermore, in step (1), the silicon-based material is one or more of elemental silicon, silicon oxide, or silicon-lithium alloy silicon-based anode materials, such as nano-silicon (100nm), micro-silicon (5μm), silicon oxide (500nm), etc.

[0009] Furthermore, in step (1), the mass ratio of the polymer precursor material to the silicon-based material is (0.01~0.5):1.

[0010] Furthermore, the mixing method in step (1) includes dry material stirring and mixing or solvent-assisted mixing followed by evaporation to remove the solvent, wherein the auxiliary solvent is one or more of water, ethanol, and acetonitrile.

[0011] 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℃, and the reaction time is 0.5~5h.

[0012] Furthermore, the reaction temperature is maintained for 0.5 to 5 hours in step (3).

[0013] Furthermore, in step (4), the mass ratio of polymer-coated silicon-based composite material, conductive agent, and binder is 50~95:2.5~25:2.5~25.

[0014] 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.

[0015] Furthermore, a polymer-coated silicon-based composite material is prepared by the above-described preparation method.

[0016] Furthermore, the prepared polymer-coated silicon-based composite material is used as a battery anode material, especially in lithium-ion batteries.

[0017] The features of this invention are as follows: First, the polymer precursor material and the silicon-based material are thoroughly mixed using dry mixing or solution-assisted mixing. Then, the precursor material molecules are uniformly attached to the surface of the silicon-based material through high-temperature evaporation, adsorption, and melting. At the reaction temperature, the precursor material molecules undergo a dehalogenation polymerization reaction, forming a uniform polymer coating layer on the surface of the silicon-based material. No other treatment is required to obtain the polymer-coated silicon-based composite material. Finally, the polymer-coated silicon-based composite material is prepared into a battery electrode sheet, which serves as the negative electrode of a lithium-ion battery.

[0018] Beneficial Effects: Compared with the prior art, the present invention has the following significant advantages: 1. The preparation method of 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 spontaneously and uniformly adsorb onto the surface of silicon-based material, which facilitates the formation of a uniform polymer coating layer with controllable thickness; 3. The precursor material has a specific molecular structure and dehalogenation polymerization sites, and the generated polymer coating layer has a specific pore structure, which facilitates the desolvation and rapid transport of ions; 4. The polymer coating layer in the present invention has high mechanical strength, which can suppress the volume expansion of silicon-based material when storing ions, prevent the breakage of active material and electrode pulverization, and effectively extend the cycle life of silicon-based anode; 5. The preparation method of 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 in cost, and suitable for large-scale production. Attached Figure Description

[0019] Figure 1 In Embodiment 1 of the present invention (Si) 100nm Scanning electron microscope (SEM) image of the sample prepared by @M1); Figure 2 In Embodiment 1 of the present invention (Si) 100nm X-ray diffraction (XRD) pattern of the sample prepared by @M1); Figure 3 In Embodiment 1 of the present invention (Si) 100nm Raman spectra of the samples prepared by @M1); Figure 4 This is a cycle performance diagram of the samples from Examples 1, 2, 3, 6 and Comparative Example 1 of this invention as lithium-ion battery electrode sheets; Figure 5 The graphs show the cycle performance of the samples from Examples 4, 5 and Comparative Example 2 of this invention as lithium-ion battery electrode sheets. Figure 6 This is a cycle performance diagram of the samples from Examples 7, 8 and Comparative Example 3 of this invention as lithium-ion battery electrode sheets. Detailed Implementation

[0020] The specific technical solution of the present invention will be further described in detail below with reference to specific examples.

[0021] In the following embodiments of the present invention, the energy storage performance test steps for polymer-coated silicon-based composite material as a negative electrode of lithium-ion battery are as follows: the prepared polymer-coated silicon-based composite material electrode sheet is used as the working electrode, the lithium metal sheet is used as the counter electrode, the electrolyte composition is "1 M LiPF6 in EC:DEC = 3:7 wt% with 10% FEC", and then charge-discharge tests are performed between 0.01-1.00V at room temperature.

[0022] Example 1: Polymer precursor material M1 and nano-silicon (100nm) were weighed at a mass ratio of 0.01:1. The two powders were poured into a mixer and thoroughly stirred and mixed to obtain a homogeneous mixture. The mixture was transferred to a high-temperature reactor filled with inert gas and heated to 520°C at a rate of 15°C / min, and held at this temperature for 2 hours to obtain a polymer-coated silicon-based composite material (Si). 100nm @M1); Si 100nm @M1 composite material was thoroughly mixed with Sup-p and CHONa in a mass ratio of 8:1:1 to form an electrode slurry, which was then coated onto copper foil to obtain a battery electrode sheet. The performance of the electrode sheet was then tested.

[0023] Example 2: Polymer precursor material M2 and nano-silicon (100nm) were weighed at a mass ratio of 0.1:1. M2 powder was poured into ethanol and fully dispersed to form a dispersion. Nano-silicon was then added and thoroughly stirred and mixed. The mixture was then dried to remove the ethanol, resulting in a homogeneous mixture. The mixture was transferred to a high-temperature reactor filled with inert gas and 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 100nm @M2 composite material is thoroughly mixed with Sup-p and CHONa in a mass ratio of 90:5:5 to form an electrode slurry. This slurry is then coated onto copper foil to obtain a battery electrode sheet, and the performance of the electrode sheet is tested.

[0024] Example 3: Polymer precursor material M4 and nano-silicon (100nm) were weighed at a mass ratio of 0.2:1. The two powders were poured into a mixer and thoroughly stirred and mixed to obtain a homogeneous mixture. The mixture was transferred to a high-temperature reactor filled with inert gas and heated 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@M4 composite material is thoroughly mixed with Ketjen Black and CHONa at a mass ratio of 80:1:1 to form an electrode slurry, which is then coated onto copper foil to obtain a battery electrode sheet. The performance of the electrode sheet is then tested.

[0025] Example 4: Polymer precursor material M6 and micron-sized silicon (5µm) were weighed at a mass ratio of 0.1:1. The two powders were poured into a mixer and thoroughly stirred and mixed to obtain a homogeneous mixture. The mixture was transferred to a high-temperature reactor filled with inert gas and heated to 600°C at a rate of 20°C / min, and held at this temperature for 3 hours to obtain a polymer-coated silicon-based composite material (Si). 5µm @M6); Si 5µm @M6 composite material was thoroughly mixed with Sup-p and CHONa in a mass ratio of 90:5:5 to form an electrode slurry. This slurry was then coated onto carbon paper to obtain a battery electrode sheet, and the performance of the electrode sheet was tested.

[0026] Example 5: Polymer precursor material M8 and micron-sized silicon (5µm) were weighed at a mass ratio of 0.4:1. The two powders were poured into a mixer and thoroughly stirred and mixed to obtain a homogeneous mixture. The mixture was transferred to a high-temperature reactor filled with inert gas and heated to 650°C at a rate of 20°C / min, and held at this temperature for 4 hours to obtain a polymer-coated silicon-based composite material (Si). 5µm @M8); Si 5µm @M8 composite material is thoroughly mixed with Ketjen Black and CHONa in a mass ratio of 60:25:15 to form an electrode slurry. This slurry is then coated onto carbon paper to obtain a battery electrode sheet, and the performance of the electrode sheet is tested.

[0027] Example 6: Polymer precursor material M9 and nano-silicon (100nm) were weighed at a mass ratio of 0.2:1. The two powders were poured into a mixer and thoroughly stirred and mixed to obtain a homogeneous mixture. The mixture was transferred to a high-temperature reactor filled with inert gas and heated 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 @M9 composite material is thoroughly mixed with Sup-p and CHONa in a mass ratio of 80:10:10 to form an electrode slurry. This slurry is then coated onto copper foil to obtain a battery electrode sheet, and the performance of the electrode sheet is tested.

[0028] Example 7: Polymer precursor material M3 and silicon dioxide (500 nm) were weighed at a mass ratio of 0.1:1. M3 powder was poured into ethanol and fully dispersed to form a dispersion. Silicon dioxide was then added and thoroughly stirred and mixed. The mixture was then dried to remove the ethanol, resulting in a homogeneous mixture. The mixture was transferred to a high-temperature reactor filled with inert gas and 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 @M3 composite material is thoroughly mixed with Sup-p and CHONa in a mass ratio of 70:20:10 to form an electrode slurry, which is then coated onto copper foil to obtain a battery electrode sheet. The performance of the electrode sheet is then tested.

[0029] Example 8: Polymer precursor material M7 and silicon dioxide (500 nm) were weighed at a mass ratio of 0.2:1. The two powders were poured into a mixer and thoroughly stirred and mixed to obtain a homogeneous mixture. The mixture was transferred to a high-temperature reactor filled with inert gas and heated 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 @M7 composite material was thoroughly mixed with Ketjen Black and CHONa in a mass ratio of 60:25:15 to form an electrode slurry, which was then coated onto carbon paper to obtain a battery electrode sheet. The performance of the electrode sheet was then tested.

[0030] Comparative Example 1: Nano-silicon (100nm) was thoroughly mixed with Sup-p and CHONa in a mass ratio of 8:1:1 to form an electrode slurry. This slurry was then coated onto copper foil to obtain a battery electrode sheet, and the performance of the electrode sheet was tested.

[0031] Comparative Example 2: Micron-sized silicon (5µm) was thoroughly mixed with Sup-p and CHONa in a mass ratio of 90:5:5 to form an electrode slurry. The slurry was then coated onto carbon paper to obtain a battery electrode sheet, and the performance of the electrode sheet was tested.

[0032] Comparative Example 3: Silicon oxide (500nm) was thoroughly mixed with Sup-p and CHONa in a mass ratio of 70:20:10 to form an electrode paste, which was then coated onto copper foil to obtain a battery electrode sheet. The performance of the electrode sheet was then tested.

[0033] In summary, the various polymer-coated silicon-based composite materials prepared by this invention are safe and pollution-free in the manufacturing process, simple to operate, and low in cost, making them suitable for large-scale production. The polymer coating layer obtained by dehalogenation polymerization in this invention suppresses the volume expansion of silicon-based materials when storing lithium ions, effectively preventing the breakage of active materials and electrode pulverization. Compared with unmodified silicon-based materials, the various polymer-coated silicon-based composite materials obtained by this invention effectively improve the cycle performance of silicon-based anodes in lithium-ion batteries.

Claims

1. A method for preparing a polymer-coated silicon-based composite material, characterized in that, The method comprises the following steps: (1) mixing the polymer precursor material and the silicon-based material in a certain proportion to obtain a uniform mixture; (2) placing the uniform mixture in an inert gas atmosphere, and heating to the dehalogenation polymerization temperature of the precursor material; (3) maintaining the reaction temperature until polymerization, forming a uniform polymer layer on the surface of the silicon-based material to obtain a polymer-coated silicon-based composite material; (4) mixing the polymer-coated silicon-based composite material with a conductive agent and a binder in a certain proportion, and then coating 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, In the step (1), the polymer precursor material is an organic molecule having a benzene ring structure and two or more halogenated aromatic groups, which is divided into two categories of halogenated six-membered aromatic ring and halogenated thiophene, including but not limited to one or more of the following structures: ； In the formula, X represents H, F, CI, Br or I; Y represents C-H or N.

3. The method for preparing a polymer-coated silicon-based composite material according to claim 1, characterized in that, In the step (1), the silicon-based material is one or more of the silicon-based negative electrode materials of 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, In the step (1), the mixing method includes dry mixing or solvent-assisted mixing followed by evaporation to remove the solvent, and 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 the step (2), the inert gas is one or more of nitrogen, argon and helium; the dehalogenation polymerization temperature is 300-700℃, and the reaction time is 0.5-5h.

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

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 method of any one of claims 1-9 as a battery negative electrode material.

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