Ionic conductor polymer coated silicon-based negative electrode material and preparation method thereof

Abstract

The invention discloses an ion conductor polymer coated silicon-based negative electrode material and a preparation method thereof. Comprising the following steps: (1) weighing an ionic conductor, and dissolving the ionic conductor in a mixed solvent composed of deionized water and ethanol; (2) adding conductive agent dispersion liquid, and performing ultrasonic treatment; (3) adding potassium persulfate as a free radical polymerization initiator; (4) adding nano silicon powder, and reacting in a water bath kettle; and (5) carrying out vacuum filtration and drying to obtain the ion conductor polymer coated silicon-based negative electrode material. The ionic conductor polymer coating layer forms a continuous and compact conductive network on the surfaces of the silicon particles, so that the overall conductivity and the electron transmission rate of the electrode are remarkably improved, efficient diffusion and migration of lithium ions on an electrode / electrolyte interface are promoted, the interface impedance is reduced, and the reversibility of electrochemical reaction is improved. The negative electrode material shows high reversible capacity and high first coulombic efficiency under low current density, and the capacity is kept at 926 mAh / g after 300 cycles under high current density.

Description

Technical Field

[0001] This invention belongs to the technical field of lithium-ion battery anode materials, specifically, it relates to a silicon-based anode material coated with an ion-conducting polymer and its preparation method. Background Technology

[0002] Lithium-ion batteries (LIBs) are widely used in portable electronic devices, electric vehicles, and energy storage systems due to their high energy density, long cycle life, and environmental friendliness. Among these applications, the electrochemical performance of the anode material plays a decisive role in the battery's specific capacity, rate performance, and cycle stability. While traditional graphite anodes exhibit excellent cycle stability, their theoretical specific capacity is only 372 mAh g⁻¹. –1 This is no longer sufficient to meet the demands of high-energy-density energy storage systems. In contrast, silicon, as a new generation of high-capacity anode material, has a theoretical specific capacity as high as 4200 mAh g⁻¹. –1 It is more than ten times larger than graphite. However, due to the volume expansion of up to about 300% during lithium-ion insertion / extraction, it leads to severe particle pulverization, electrode structure collapse and active material shedding, resulting in a sharp decline in cycle life and electrochemical performance.

[0003] To address this issue, researchers have proposed various strategies to mitigate volume expansion and stabilize the solid electrolyte interface (SEI), including nanostructure design, surface modification, and carbon composites. However, the fabrication of complex nanostructures or surface modification often leads to increased costs, and achieving a balance between material elasticity and mechanical strength is difficult, potentially causing structural failure during cycling. In contrast, constructing functionalized interface coatings on silicon particle surfaces is an effective engineering approach that can enhance structural stability while passivating the active interface and promoting Li... + Uniform diffusion. In particular, the use of a conductive electron-ion composite coating as a surface coating layer can not only improve the overall conductivity and ion conduction capability of the electrode, but also provide a flexible buffer to adapt to volume changes during charging and discharging.

[0004] Based on this, the present invention proposes a method for preparing a silicon-based anode coated with an ion-conducting polymer suitable for lithium-ion batteries. This method can form a stable and dense conductive electron-ion composite coating layer in situ on the silicon surface, effectively improving the electron and ion transport capabilities of the electrode, thereby significantly improving the cycle performance, rate characteristics, and overall reliability of the silicon-based anode, providing a feasible technical solution for the development of high-energy-density lithium-ion batteries. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a silicon-based anode material coated with an ion-conducting polymer based on thermally initiated free radical polymerization and its preparation method. This method can construct a stable and dense composite coating layer of conductive electrons and ions in situ on the surface of silicon particles, effectively mitigating the volume expansion of silicon during charging and discharging, significantly improving its ability to conduct electrons and ions, thereby enhancing the initial coulombic efficiency and rate performance of silicon-based anodes in lithium-ion batteries.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing a silicon-based anode material coated with an ion-conducting polymer includes the following steps:

[0008] (1) Weigh out the ionic conductor, dissolve it in a mixed solvent of deionized water and ethanol, and stir until homogeneous;

[0009] (2) Add conductive agent dispersion to the above solution and obtain a uniform and stable suspension by ultrasonic treatment;

[0010] (3) Add potassium persulfate as a free radical polymerization initiator and continue stirring to mix it thoroughly;

[0011] (4) Add nano-silicon powder, stir evenly, and then place the system in a water bath to react so as to achieve in-situ coating of ion conductor polymer on silicon surface.

[0012] (5) After the reaction is completed, the product is recovered by vacuum filtration and then dried to obtain silicon-based anode material coated with ion conductor polymer;

[0013] The ion conductor is any one of hexafluorobutyl methacrylate, ethylene glycol methyl ether methacrylate, sodium p-styrene sulfonate, potassium isopropenyl trifluoroborate, 2-acrylamido-2-methylpropanesulfonic acid, or sodium methacrylate.

[0014] Preferably, in the preparation method of the silicon-based anode material coated with the ion conductor polymer described above, the mass ratio of the nano-silicon powder, ion conductor and conductive agent in step (1) is 1:1 to 5:0.0075 to 0.0125.

[0015] Preferably, in the preparation method of the silicon-based anode material coated with the above-mentioned ion conductor polymer, the conductive agent is any one of graphene oxide, carbon black, Ketjen black, or carbon nanotubes.

[0016] Preferably, in the preparation method of the silicon-based anode material coated with the above-mentioned ion conductor polymer, the volume ratio of deionized water and ethanol in the mixed solvent in step (1) is 1-5:0.5-1.5.

[0017] Preferably, in the preparation method of the silicon-based anode material coated with the ion conductor polymer described above, the amount of potassium persulfate added in step (3) is 0.1-0.3% of the weight of the ion conductor.

[0018] Preferably, in the preparation method of the silicon-based anode material coated with the above-mentioned ion conductor polymer, the temperature of the water bath in step (4) is 60-80℃.

[0019] A method for preparing a silicon-based anode sheet includes the following steps: weighing silicon-based anode material coated with the ion conductor polymer of claim 1, carboxymethyl cellulose and conductive carbon black in a mass ratio of 7:2:1, dispersing them in an aqueous solution and stirring magnetically for 12 hours, uniformly coating them onto a copper foil current collector using a coating machine, pre-drying them and then vacuum drying them to obtain the silicon-based anode sheet.

[0020] A silicon-based anode material coated with an ion-conducting polymer is prepared using the above-described preparation method.

[0021] A lithium-ion battery includes a negative electrode material, said negative electrode material comprising a silicon-based negative electrode material coated with the aforementioned ion-conducting polymer.

[0022] The beneficial effects of this invention are as follows:

[0023] (1) Improved conductivity and ion transport efficiency: The ion-conducting polymer coating forms a continuous and dense conductive network on the surface of silicon particles, which significantly improves the overall conductivity and electron transport rate of the electrode, promotes the efficient diffusion and migration of lithium ions at the electrode / electrolyte interface, thereby reducing interfacial impedance and improving the reversibility of the electrochemical reaction. Therefore, this anode material exhibits high reversible capacity (2744 mAh / g) and high initial coulombic efficiency (91.6%) at low current density, and maintains a capacity of 926 mAh / g after 300 cycles at high current density.

[0024] (2) Alleviating volume expansion and enhancing structural stability: The ion-conducting polymer coating layer can serve as a flexible buffer layer, effectively mitigating the pulverization and electrode structure damage caused by the drastic volume expansion of silicon during charging and discharging, maintaining the integrity of the conductive network and interface stability, and significantly improving the structural stability and cycle life of the silicon-based anode. The resulting material has uniform and stable coating, good conductivity and structural integrity, and can significantly improve the continuity of the conductive network and electrode stability of the silicon anode during cycling, making it suitable for the construction of anodes for high-performance lithium-ion batteries.

[0025] (3) Simple process and scalable preparation: The preparation method proposed in this invention is simple to operate, low in cost, mild in process, and highly controllable, making it suitable for the large-scale production of silicon-based anode materials. Its preparation process does not require complex equipment or harsh conditions, has good repeatability and consistency, and shows broad prospects for engineering and industrial applications. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the preparation process of the ion conductor polymer-coated silicon-based anode material provided by the present invention.

[0027] Figure 2 The structural evolution of the electrodes in Examples 1, 2, 3 and Comparative Example 1 before and after 50 cycles is shown.

[0028] Figure 3 The first charge-discharge curves of the silicon-based anode materials prepared in Examples 1, 2, 3 and Comparative Example 1 as anodes of lithium-ion batteries are shown.

[0029] Figure 4 The graphs show the cycling performance of silicon-based anode materials prepared in Examples 1, 2, 3 and Comparative Example 1 as lithium-ion battery anodes under high current density.

[0030] Figure 5 The graph shows the rate performance of silicon-based anode materials prepared in Examples 1, 2, 3 and Comparative Example 1 as anodes in lithium-ion batteries.

[0031] Figure 6 The GITT diagrams are of the silicon-based anode materials prepared in Examples 1, 2, 3 and Comparative Example 1 as anodes for lithium-ion batteries. Detailed Implementation

[0032] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings. These embodiments are only some, not all, of the present invention. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the art.

[0033] Example 1:

[0034] (1) Weigh 0.6g of sodium p-styrene sulfonate (NaSS), dissolve it in a mixed solvent of 4mL deionized water and 1mL ethanol, stir evenly, then add 1mL of graphene oxide (GO) dispersion with a concentration of 2mg / mL, and obtain a uniform and stable black suspension by ultrasonic treatment. Then add 0.012g of potassium persulfate (K2S2O8) as a free radical initiator and stir evenly. Then add 0.2g of nano silicon powder (Si), continue to stir and mix, and place the reaction system in a 70℃ water bath for 12h to achieve in-situ coating of polymer on Si surface;

[0035] (2) After the reaction was completed, the product was collected by vacuum filtration and dried at 70°C for 12 hours to obtain a silicon-based composite material with an ion conductor polymer layer on the surface.

[0036] (3) 70 mg of the silicon-based anode material prepared in this example, 20 mg of sodium carboxymethyl cellulose (CMC) and 10 mg of conductive carbon black were mixed in a mass ratio, and an appropriate amount of deionized water was added to make a slurry. After magnetic stirring for 12 h, the slurry was uniformly coated onto copper foil. After drying the coating at 90 °C for 12 h, a silicon-based anode sheet was obtained.

[0037] (4) Using lithium metal sheets as the counter electrode, CR2032 button cells were assembled in a glove box filled with argon gas (H2O, O2<0.1ppm) for subsequent electrochemical performance testing.

[0038] Example 2:

[0039] (1) Weigh 0.625g of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), dissolve it in a mixed solvent of 4mL deionized water and 1mL ethanol, stir evenly, then add 1mL of graphene oxide (GO) dispersion with a concentration of 2mg / mL, and obtain a uniform and stable black suspension by ultrasonic treatment. Then add 0.012g of potassium persulfate (K2S2O8) as a free radical initiator and stir evenly. Then add 0.2g of nano-silicon powder (Si), continue to stir and mix, and place the reaction system in a 70℃ water bath for 12h to achieve in-situ coating of polymer on Si surface;

[0040] (2) After the reaction is complete, the product is vacuum filtered and then dried in a vacuum drying oven at 70°C for 12 hours to obtain a silicon-based material with a surface coated with an ion conductor polymer.

[0041] (3) The electrode preparation and electrochemical testing methods are the same as in Example 1.

[0042] Example 3:

[0043] (1) Weigh 0.625g sodium methacrylate (NaMAA), dissolve it in a mixed solvent of 4mL deionized water and 1mL ethanol, stir evenly, then add 1mL of graphene oxide (GO) dispersion with a concentration of 2mg / mL, and obtain a uniform and stable black suspension by ultrasonic treatment. Then add 0.012g potassium persulfate (K2S2O8) as a free radical initiator and stir evenly. Then add 0.2g of nano silicon powder (Si), continue to stir and mix, and place the reaction system in a 70℃ water bath for 12h to achieve in-situ coating of polymer on Si surface;

[0044] (2) After the reaction is complete, the product is vacuum filtered and then dried in a vacuum drying oven at 70°C for 12 hours to obtain a silicon-based material with a surface coated with an ion conductor polymer.

[0045] (3) The electrode preparation and electrochemical testing methods are the same as in Example 1.

[0046] Comparative Example 1:

[0047] For the control experiment, no polymer coating was performed.

[0048] A control electrode was prepared by mixing 70 mg of nano-silicon powder, 20 mg of carboxymethyl cellulose, and 10 mg of conductive carbon black in a specific ratio and coating the mixture onto copper foil. The mixture was then dried in an oven at 90 °C for 12 h. A lithium metal sheet was used as the working electrode in an argon-filled glove box (H₂O, O₂ < 0.1 ppm). Electrochemical measurements of the silicon-based anode material were performed using a CR2032 coin cell.

[0049] Table 1

[0050]

[0051] Data from the GITT test, such as Figure 6 As shown, the GITT test verified its excellent kinetic characteristics. Example 1 at 0.2 A·g -1 The lithium-ion diffusion coefficient log D obtained from the test ranged from -9.47 to -13.36, which is about an order of magnitude higher than that of Comparative Example 1 (-10.30 to -14.54).

[0052] The material of this invention exhibits good structural stability, which can be verified by SEM results before and after cycling. Figure 2 This can be proven by the cycle life curve ( ), while the cycle life can be determined based on the cycle performance curve ( ). Figure 3 A comparative evaluation was conducted. Figure 2 SEM images show that before cycling, the electrode surface exhibits a uniform particle distribution, dense structure, and no obvious cracks, demonstrating excellent initial structural integrity. After 50 cycles, although slight cracks appeared in the silicon particles of Example 1, the overall structure remained intact, with no obvious pulverization or peeling observed, indicating that the designed composite structure can effectively mitigate the volume expansion of silicon during charge and discharge. In contrast, the electrode surface of Comparative Example 1 showed severe pulverization, with cracks penetrating the entire electrode layer, significantly damaging the conductive network. A comprehensive comparison shows that the sample of Example 1 is significantly superior to Comparative Example 1 in terms of structural integrity, indicating that this composite system has a significant advantage in maintaining electrode structural stability and conductive continuity.

[0053] Regarding electrochemical performance, Example 1 at 3A·g -1 The initial discharge specific capacity at current density is 2133 mAh·g-1 It still maintains 926 mAh·g after 300 cycles. -1 The corresponding capacity retention rate is 43.4%, and the average coulombic efficiency is as high as 99.8%. These results indicate that the electrode system exhibits excellent reversibility and cycling stability, demonstrating a longer cycle life. Compared with the rapid capacity decay commonly seen in traditional silicon-based electrodes, this material system can maintain stable ion and electron transport channels during long cycles, demonstrating significant structural stability and electrochemical durability.

Claims

1. A method for preparing a silicon-based anode material coated with an ion-conducting polymer, characterized in that, Includes the following steps: (1) Weigh out the ionic conductor, dissolve it in a mixed solvent of deionized water and ethanol, and stir until homogeneous; (2) Add conductive agent dispersion to the above solution and obtain a uniform and stable suspension by ultrasonic treatment; (3) Add potassium persulfate as a free radical polymerization initiator and continue stirring to mix it thoroughly; (4) Add nano-silicon powder, stir evenly, and then place the system in a water bath to react so as to achieve in-situ coating of ion conductor polymer on silicon surface. (5) After the reaction is completed, the product is recovered by vacuum filtration and then dried to obtain silicon-based anode material coated with ion conductor polymer; The ion conductor is any one of hexafluorobutyl methacrylate, ethylene glycol methyl ether methacrylate, sodium p-styrene sulfonate, potassium isopropenyl trifluoroborate, 2-acrylamido-2-methylpropanesulfonic acid, or sodium methacrylate.

2. The method for preparing the silicon-based anode material coated with an ion-conducting polymer as described in claim 1, characterized in that, The mass ratio of nano-silicon powder, ionic conductor and conductive agent in step (1) is 1:1 to 5:0.0075 to 0.0125.

3. The method for preparing the silicon-based anode material coated with an ion-conducting polymer as described in claim 1, characterized in that, The conductive agent is any one of graphene oxide, carbon black, Ketjen black, or carbon nanotubes.

4. The method for preparing the silicon-based anode material coated with an ion-conducting polymer as described in claim 1, characterized in that... In the mixed solvent of step (1), the volume ratio of deionized water to ethanol is 1-5:0.5-1.

5.

5. The method for preparing the silicon-based anode material coated with an ion-conducting polymer as described in claim 1, characterized in that... The amount of potassium persulfate added in step (3) is 0.1-0.3% of the weight of the ionic conductor.

6. The method for preparing the silicon-based anode material coated with an ion-conducting polymer as described in claim 1, characterized in that... The temperature of the water bath in step (4) is 60-80℃.

7. A method for preparing a silicon-based negative electrode, characterized in that... The process includes the following steps: Weigh the silicon-based anode material coated with the ion conductor polymer of claim 1, carboxymethyl cellulose and conductive carbon black in a mass ratio of 7:2:1, disperse them in an aqueous solution and stir magnetically for 12 hours, coat them evenly on a copper foil current collector using a coating machine, and then vacuum dry them after preliminary drying to obtain a silicon-based anode sheet.

8. A silicon-based anode material coated with an ion-conducting polymer, characterized in that, It is prepared by any one of the preparation methods described in claims 1 to 6.

9. A lithium-ion battery, comprising a negative electrode material, characterized in that... The negative electrode material includes the silicon-based negative electrode material coated with the ion conductor polymer as described in claim 8.

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