Conductive polymer-coated photovoltaic waste silicon material, method of making and lithium battery

Abstract

This invention relates to the field of new energy materials technology, specifically to conductive polymer-coated photovoltaic waste silicon materials, their preparation methods, and lithium batteries. The process involves pretreating photovoltaic waste silicon to obtain nano-silicon powder particles; subsequently, selective interface modification is performed to obtain modified nano-silicon powder particles; using the modified nano-silicon powder particles as a matrix, conductive polymer monomers are coated onto them, and an initiator and binder are added, resulting in an in-situ polymerization reaction to form a conductive polymer coating layer structure, thus obtaining the conductive polymer-coated photovoltaic waste silicon material. This invention, through a synergistic strategy of interface modification and conductive polymer coating, alleviates the volume expansion of silicon anodes, improves conductivity, and exhibits stable cycle performance and good rate adaptability. The required raw materials are derived from photovoltaic waste silicon, reducing costs and pollution. Furthermore, the preparation process is simple and produces uniform coating, providing a new path for the low-cost commercial application of silicon-based anodes in lithium batteries.

Description

Technical Field

[0001] This invention relates to the field of new energy materials technology, specifically to photovoltaic waste silicon materials coated with conductive polymers, their preparation methods, and lithium batteries. Background Technology

[0002] Photovoltaic waste silicon, as an important solid waste resource in the photovoltaic industry, is characterized by abundant output and low cost. However, traditional landfilling and other methods result in significant environmental pollution and resource waste. If it can be recycled into lithium-ion battery anode materials at a high value, it can solve the solid waste problem, reduce the cost of silicon anode raw materials, and achieve both economic and ecological benefits.

[0003] However, the commercial application of silicon anodes in lithium-ion batteries remains challenging due to their significant volume expansion and poor conductivity. It is noteworthy that photovoltaic waste silicon particles possess an oxide layer on their surface, exhibiting electronegativity. A conductive polymer coating layer can be constructed through chemical bonding, which can not only suppress silicon volume expansion but also increase the material's conductivity. In existing technologies, Guan Lun-hui et al. (XU Jin-Jian, WU Wang-Liang, GUAN Lun-Hui. Synthesis of Three-Dimensional Porous Interconnected Hollow Carbon Nanosphere Arrays and Its Application in Lithium-Sulfur Batteries. Chinese J. Struct. Chem., 2017.10 Vol.36, No.10) designed a carbon nanotube / polymer conductive network (PAA-TA-CMC / CNT). This network forms a dense conductive network through the self-assembly of carboxymethyl cellulose (CMC) and carboxylated multi-walled carbon nanotubes (CNTs). Polyacrylic acid (PAA) and tannic acid (TA) are used as binders, and covalent and hydrogen bonds are employed to enhance coating adhesion, achieving a certain degree of conductive coating and structural stability of the silicon particles. However, if the above method is directly applied to photovoltaic waste silicon, the following problems still exist: silicon may still undergo expansion of up to 300% during lithiation, leading to cracking or detachment of the coating layer, damaging the integrity of the electrode structure, and causing repeated rupture and repair of the solid electrolyte interphase (SEI) membrane, consuming electrolyte and active lithium, and reducing cycle life. In addition, the inherent conductivity of the polymer coating layer is limited, making it difficult to quickly complete charge transfer during high-rate charge and discharge, thus limiting rate performance. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a conductive polymer-coated photovoltaic waste silicon material, its preparation method, and its applications. This invention employs a dual protection mechanism of selective interface modification and conductive polymer coating. The coating layer adapts to the volume changes during charging and discharging, preventing direct contact between silicon and the electrolyte. The interface modification layer forms a stable structure on the silicon surface. Together, these two mechanisms mitigate the risks associated with volume expansion, improving material cycle stability, extending battery life, and maintaining high capacity. Furthermore, this invention utilizes the excellent conductivity of the conductive polymer to construct an efficient electron transport channel for the silicon-based anode, accelerating charge transfer, reducing battery internal resistance, and thereby improving the battery's charging and discharging efficiency and power performance, meeting the requirements for high-rate operation. This solves the problems of existing conductive polymer coating processes where silicon anode volume expansion damages the electrode structure, resulting in short lifespan and poor conductivity, thus limiting rate performance.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: The first objective of this invention is to provide a method for preparing a conductive polymer-coated photovoltaic waste silicon material, comprising the following steps: S1. Pre-treat photovoltaic waste silicon to obtain nano-silicon powder particles.

[0006] S2. Add a silane coupling agent to the nano-silicon powder particles to selectively modify the interface, and graft organic functional group molecular chains onto the surface of the nano-silicon powder particles to obtain modified nano-silicon powder particles.

[0007] S3. Using modified nano-silicon powder particles as the matrix, a conductive polymer monomer is coated on it. An initiator and a binder are added to induce the conductive polymer monomer to undergo an in-situ polymerization reaction at the interface of the modified nano-silicon powder particles, forming a conductive polymer coating layer structure, and thus obtaining a conductive polymer-coated photovoltaic waste silicon material.

[0008] In a preferred embodiment of the present invention, the molar ratio of modified nano-silicon powder particles to conductive polymer monomers is 7:1, and the conductive polymer monomers are at least one of pyrrole and aniline.

[0009] In a preferred embodiment of the present invention, the mass ratio of modified nano-silicon powder particles to initiator is 1:10, and the initiator is ammonium persulfate.

[0010] In a preferred embodiment of the present invention, the mass ratio of modified nano-silica powder particles to binder is 6~7:1~2, and the binder is carboxymethyl cellulose.

[0011] In a preferred embodiment of the present invention, the in-situ polymerization reaction takes 8 to 12 hours and the temperature is -5°C to 5°C.

[0012] In a preferred embodiment of the present invention, the mass ratio of the silane coupling agent to the nano-silicon powder particles is 10:1, and the silane coupling agent is at least one of KH550, KH560, and KH570.

[0013] In a preferred embodiment of the present invention, the selective interface modification reaction temperature is 70℃~90℃ and the reaction time is 5h~7h.

[0014] The second objective of this invention is to provide a photovoltaic waste silicon material coated with a conductive polymer obtained by the above method.

[0015] A third objective of this invention is to provide a lithium battery comprising a positive electrode, a negative electrode, and an electrolyte; the negative electrode is a photovoltaic waste silicon material coated with the aforementioned conductive polymer.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention provides a method for preparing photovoltaic waste silicon material coated with conductive polymer. The method involves pretreating photovoltaic waste silicon to obtain nano-silicon powder particles, followed by selective interface modification by grafting organic functional group molecular chains onto the surface of the nano-silicon powder particles to obtain modified nano-silicon powder particles. Using the modified nano-silicon powder particles as a matrix, conductive polymer monomers are coated onto them. An initiator and binder are added to induce in-situ polymerization of the conductive polymer monomers at the interface of the modified nano-silicon powder particles, forming a conductive polymer coating layer structure, thus obtaining the conductive polymer-coated photovoltaic waste silicon material. This invention employs a dual protection mechanism of conductive polymer coating layer + interface modification layer. The coating layer can adapt to volume changes during charging and discharging, avoiding direct contact between silicon and electrolyte; the interface modification layer forms a stable structure on the silicon surface. Together, they resist the risks of cracking and detachment caused by volume expansion, significantly improving the material's cycle stability, extending battery life, and maintaining high capacity. Furthermore, this invention utilizes the excellent conductivity of the conductive polymer itself to construct an efficient electron transport channel for the silicon-based negative electrode, accelerating charge transfer, reducing battery internal resistance, and thus improving the battery's charging and discharging efficiency and power performance, meeting the requirements for high-rate use. Finally, the coating layer isolates the silicon from direct contact with the electrolyte, reducing side reactions and lowering the risk of thermal runaway; the stable interface layer can inhibit lithium dendrite growth, preventing it from piercing the separator and causing a short circuit, thus greatly improving the reliability and safety of the battery.

[0017] 2. This invention utilizes recycled photovoltaic waste silicon, which is processed into nano-silicon particles through crushing and refining. This reduces the application cost of nano-silicon particles and enhances the utilization value of photovoltaic waste silicon. By combining interface control strategies with the oxidation characteristics of the waste silicon surface, interface modifiers are selectively used to achieve one-step elemental doping to improve conductivity, avoiding complex polymer coating and doping processes, simplifying the preparation process and reducing costs. The invention focuses on achieving uniformity and consistency of conductive polymer coating, and innovatively adopts a "selective interface control doping-conductive polymer" synergistic strategy. This overcomes the problems of poor conductive polymer coating, short electrochemical cycle life, and poor conductivity, ultimately achieving low-cost application of silicon-based anode materials and improving the reuse value of photovoltaic solid waste.

[0018] 2. This invention provides a conductive polymer-coated photovoltaic waste silicon material. It employs an interface modifier containing nitrogen and other elements to selectively regulate the interface of the photovoltaic waste silicon, and introduces the conductive polymer coating structure into the silicon-based anode system to prepare a lithium-ion battery silicon-based anode material with long cycle performance and high conductivity. It has the following advantages: First, the conductive polymer coating layer can adapt to the volume changes of the silicon-based anode during charge and discharge, avoiding direct contact between the material and the electrolyte, and reducing structural damage caused by volume expansion. The interface modifier containing nitrogen and other elements can form a stable interface layer on the silicon surface, further enhancing the structural stability. This dual protection mechanism can significantly improve the cycle stability of the silicon-based anode material, extend the battery's lifespan, and enable the battery to maintain a high capacity even after multiple charge and discharge cycles. Second, the conductive polymer has good conductivity, providing an efficient electron transport channel for the silicon-based anode and improving the overall conductivity of the material. When the conductive polymer coating structure is introduced into the silicon-based anode system, electrons can conduct more quickly and smoothly in the electrode material, reducing the battery's internal resistance, thereby improving the battery's charge and discharge efficiency and power performance. Third, the coating layer prevents direct contact between silicon and the electrolyte, reducing side reactions and the risk of battery thermal runaway. A stable interface layer inhibits lithium dendrite growth, preventing short circuits and other safety issues caused by lithium dendrites piercing the separator, making the battery more reliable and safer during use. Fourth, high-energy-density batteries can provide longer battery life, significantly increasing the driving range of vehicles, such as in the new energy vehicle sector; and extending the lifespan of devices like mobile phones and tablets in the consumer electronics sector. Attached Figure Description

[0019] Figure 1 This is a SEM image of the photovoltaic waste silicon nanoparticles from Example 1 of the present invention.

[0020] Figure 2 The image shows the XRD pattern of photovoltaic waste silicon nanoparticles from Example 1 of this invention.

[0021] Figure 3This is the infrared spectrum of selective interface modulation of photovoltaic waste silicon in Example 1 of the present invention.

[0022] Figure 4 The graph shows the constant current charge-discharge cycle performance of the electrode sheet of the present invention at a current of 200 mA / g.

[0023] Figure 5 This is a graph showing the charge / discharge rate performance of the battery active material of the present invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] It should be noted that the technical terms used in this invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0026] Existing methods for preparing conductive polymer-coated waste silicon anode materials require complex chemical experiments, resulting in poor coating uniformity and structural consistency, leading to low efficiency. Therefore, this invention leverages the electronegativity of waste silicon surface and selectively utilizes interface control to achieve maximum conductivity doping through direct manipulation. This simplifies the process, provides uniform structure, conserves photovoltaic waste resources, reduces energy consumption for enterprises, and offers a new approach for developing novel lithium-ion battery anode materials.

[0027] First, this invention provides a method for preparing a conductive polymer-coated photovoltaic waste silicon material, comprising the following steps: S1. Pretreatment of photovoltaic waste silicon (purification and particle refinement): The recycled photovoltaic silicon cutting waste is subjected to flotation, acid washing, and mechanical grinding and crushing to achieve a particle size of nanoscale, thus obtaining nano-silicon powder particles.

[0028] The specific process is as follows: the recovered photovoltaic silicon cutting waste is floated to remove metal debris and cutting fluid residue, the oxides are dissolved by acid washing to purify the silicon particles, and the particles are mechanically ground and crushed to D50<100nm so that the particle size reaches the nanoscale, thus obtaining nano silicon powder particles.

[0029] S2, Selective Interface Modification: Selective interfacial modification of nano-silicon powder particles was performed by grafting organic functional group molecular chains onto the surface of the nano-silicon powder particles to obtain modified nano-silicon powder particles. Specifically, the surface polarity of the nano-silicon powder particles was analyzed using a Zeta potential analyzer and XPS, and the electronegativity of the silicon particle surface was enhanced by using hydrogen peroxide solution. Interfacial modulation was achieved by selecting silane coupling agents with different functional groups to link different types of organic functional group molecular chains onto the silicon particle surface, resulting in modified nano-silicon powder particles.

[0030] The selective interface modification employs a silane coupling agent, wherein the mass ratio of the silane coupling agent to the nano-silicon powder particles is 10:1. The silane coupling agent is at least one selected from KH550, KH560, and KH570, preferably KH550. The interface modification reaction temperature is 70℃~90℃, preferably 80℃, and the reaction time is 5h~7h, preferably 5h.

[0031] The specific process is as follows: First, the surface polarity of the nano-silicon powder particles is analyzed using a Zeta potential analyzer and XPS. Then, the nano-silicon powder particles are added to a hydrogen peroxide solution and stirred to enhance the electronegativity of the silicon particle surface, resulting in nano-silicon powder particles with enhanced electronegativity. Subsequently, the nano-silicon powder particles with enhanced electronegativity are mixed with KH550 and stirred at 80℃ for 5 hours to obtain modified nano-silicon powder particles.

[0032] The hydrogen peroxide solution has a volume of 1 mL, a concentration of 30 wt%, and a stirring time of 30 min.

[0033] S3, Cross-linking coupling of conductive polymer monomers: By combining interfacial modulation of different organic functional groups linked on the surface of modified nano-silica powder particles, specific conductive polymer monomers are selected to match (usually polymer monomers containing elements such as N and P, such as pyrrole and aniline). The conductive polymer monomer is at least one of pyrrole and aniline, preferably pyrrole.

[0034] The specific process is as follows: In an ice-water bath (-5℃~5℃), citric acid (CA) is added to pyrrole (Py), wherein the molar ratio of Py to CA is 5:3. The mixture is stirred evenly to obtain a CA-Py solution.

[0035] S4. Conductive polymer-coated photovoltaic waste silicon material: An initiator is used to induce in-situ polymerization of polymer monomers at the interface of modified nano-silicon powder particles to form a conductive polymer coating layer structure, thereby obtaining photovoltaic waste silicon material coated with conductive polymer.

[0036] The in-situ polymerization reaction takes 8-12 hours and is carried out at a temperature of -5°C to 5°C. The molar ratio of the modified silica nanoparticles to the conductive polymer monomer is 7:1, and the mass ratio of the modified silica nanoparticles to the initiator is 1:10. The initiator is ammonium persulfate. The mass ratio of the modified silica nanoparticles to the binder is 6-7:1-2, and the binder is carboxymethyl cellulose.

[0037] The specific process is as follows: Carboxymethyl cellulose (CMC) is dispersed in deionized water and stirred at 60°C for 4 hours until completely dissolved, forming a homogeneous viscous solution. This solution is then cooled to room temperature to obtain a CMC solution. Ammonium persulfate (APS) is added, and stirring continues until dissolved to obtain an APS solution. Next, the CA-Py solution and APS solution are mixed, followed by the addition of modified nano-silicon powder particles. The mixture is reacted at 5°C for 10 hours to obtain a conductive polymer-coated photovoltaic waste silicon material.

[0038] It should be noted that existing technologies using simple conductive polymer coatings have limited electron transport capabilities, failing to meet the high-rate charge-discharge requirements of lithium-ion batteries. This invention, while employing conductive polymer coating, uses interface modifiers containing elements such as nitrogen to selectively regulate the interface of photovoltaic waste silicon. The introduction of nitrogen and other elements increases the electron cloud density and improves electron mobility, thereby significantly enhancing the material's conductivity and better meeting the requirements for rapid electron transport during high-rate charge-discharge of lithium batteries. Furthermore, some existing technologies for preparing silicon-based anode materials are costly and require high purity silicon raw materials. This invention utilizes photovoltaic waste silicon as a raw material, recycling and reusing what was originally waste, reducing the preparation cost of silicon-based anode materials and achieving high-value utilization of solid waste resources, resulting in significant environmental and economic benefits. This invention employs interface modifiers containing elements such as nitrogen for selective interface regulation and introduces a conductive polymer coating structure. The interface modifier can chemically react with the silicon surface to form a special interface structure, improving the interfacial compatibility between silicon and the conductive polymer and promoting electron and lithium-ion transport. Meanwhile, the conductive polymer coating layer can not only alleviate volume expansion, but also work synergistically with the interface modification layer to improve the conductivity and lithium-ion transport capacity of the material, thereby enhancing the overall performance of the silicon-based anode of lithium batteries.

[0039] Secondly, the present invention provides a photovoltaic waste silicon material coated with a conductive polymer obtained by the above method.

[0040] Finally, the present invention provides a lithium battery, which is composed of a positive electrode, a negative electrode and an electrolyte; the negative electrode is a photovoltaic waste silicon material coated with the above-mentioned conductive polymer.

[0041] The lithium battery manufacturing process involves taking a mixture, adding a binder and acetylene black, grinding it in N-methylpyrrolidone (NMP) solvent, adding styrene-butadiene rubber, cutting copper foil, applying a sample, and finally assembling the battery.

[0042] The following specific examples will provide further explanation.

[0043] In this invention, the abbreviation for carboxymethyl cellulose is CMC, the abbreviation for pyrrole is Py, the abbreviation for citric acid is CA, the abbreviation for ammonium persulfate is APS, and the abbreviation for N-methylpyrrolidone is NMP.

[0044] Example 1 A method for preparing a conductive polymer-coated photovoltaic waste silicon material includes the following steps: S1. Photovoltaic waste silicon purification and particle refinement: The recovered photovoltaic crystalline silicon cutting waste is floated to remove metal debris and cutting fluid residue, acid washing dissolves oxides to purify silicon particles, and mechanical grinding crushes to D50<100nm, so that the particle size reaches the nanoscale, to obtain nano silicon powder particles.

[0045] S2. Selective Interface Modification: First, the surface polarity of the nano-silicon powder particles was analyzed using a Zeta potential analyzer and XPS. The nano-silicon powder particles were then added to 1 mL of a 30 wt% hydrogen peroxide solution and stirred for 30 min to enhance the electronegativity of the silicon particle surface, resulting in nano-silicon powder particles with enhanced electronegativity. Subsequently, 0.2 g of the electronegatively enhanced nano-silicon powder particles were mixed with 2 mL of KH550 and stirred at 80 °C for 5 h to obtain modified nano-silicon powder particles.

[0046] S3. Crosslinking and coupling of conductive polymer monomers: In an ice-water bath, 0.0166 g of CA was added to 10 μL of Py, wherein the molar ratio of Py to CA was 5:3. The mixture was stirred until homogeneous to obtain a CA-Py solution.

[0047] S4. Preparation of conductive polymer-coated waste silicon composite material: 0.12 g of CMC was dispersed in 5 mL of deionized water and stirred at 60 °C for 4 h until completely dissolved, forming a homogeneous viscous solution. The solution was cooled to room temperature to obtain a CMC solution. Then, 0.02 g of APS was added, and stirring continued until dissolved to obtain an APS solution. Next, the CA-Py solution and the APS solution were mixed, followed by the addition of 0.2 g of modified nano-silicon powder particles. The mixture was reacted at 5 °C for 10 h to obtain a conductive polymer-coated photovoltaic waste silicon material.

[0048] Example 2 The difference from Example 1 is that the temperature in the CMC solution preparation was 25°C, and the stirring time was 12 hours. The specific process is as follows:

[0049] S1. Photovoltaic waste silicon purification and particle refinement: The recovered photovoltaic crystalline silicon cutting waste is floated to remove metal debris and cutting fluid residue, acid washing dissolves oxides to purify silicon particles, and mechanical grinding crushes to D50<100nm, so that the particle size reaches the nanoscale, to obtain nano silicon powder particles.

[0050] S2. Selective Interface Modification: First, the surface polarity of the nano-silicon powder particles was analyzed using a Zeta potential analyzer and XPS. The nano-silicon powder particles were then added to 1 mL of a 30 wt% hydrogen peroxide solution and stirred for 30 min to enhance the electronegativity of the silicon particle surface, resulting in nano-silicon powder particles with enhanced electronegativity. Subsequently, 0.2 g of the electronegatively enhanced nano-silicon powder particles were mixed with 2 mL of KH550 and stirred at 80 °C for 5 h to obtain modified nano-silicon powder particles.

[0051] S3. Crosslinking and coupling of conductive polymer monomers: In an ice-water bath, 0.0166 g of CA was added to 10 μL of Py, wherein the molar ratio of Py to CA was 5:3. The mixture was stirred until homogeneous to obtain a CA-Py solution.

[0052] S4. Preparation of conductive polymer-coated waste silicon composite material: 0.12 g of CMC was dispersed in 5 mL of deionized water and stirred at 25 °C for 12 h until completely dissolved, forming a homogeneous viscous solution. The solution was cooled to room temperature to obtain a CMC solution. Then, 0.02 g of APS was added, and stirring continued until dissolved to obtain an APS solution. Next, the CA-Py solution and the APS solution were mixed, followed by the addition of 0.2 g of modified nano-silicon powder particles. The mixture was reacted at 5 °C for 10 h to obtain a conductive polymer-coated photovoltaic waste silicon material.

[0053] Example 3 The difference from Example 1 is that in step S2, the stirring temperature is 85°C and the stirring time is 4.5 hours. The specific process is as follows:

[0054] S1. Photovoltaic waste silicon purification and particle refinement: The recovered photovoltaic crystalline silicon cutting waste is floated to remove metal debris and cutting fluid residue, acid washing dissolves oxides to purify silicon particles, and mechanical grinding crushes to D50<100nm, so that the particle size reaches the nanoscale, to obtain nano silicon powder particles.

[0055] S2. Selective Interface Modification: First, the surface polarity of the nano-silicon powder particles was analyzed using a Zeta potential analyzer and XPS. The nano-silicon powder particles were then added to 1 mL of a 30 wt% hydrogen peroxide solution and stirred for 30 min to enhance the electronegativity of the silicon particle surface, resulting in nano-silicon powder particles with enhanced electronegativity. Subsequently, 0.2 g of the electronegatively enhanced nano-silicon powder particles were mixed with 2 mL of KH550 and stirred at 85 °C for 4.5 h to obtain modified nano-silicon powder particles.

[0056] S3. Crosslinking and coupling of conductive polymer monomers: In an ice-water bath, 0.0166 g of CA was added to 10 μL of Py, wherein the molar ratio of Py to CA was 5:3. The mixture was stirred until homogeneous to obtain a CA-Py solution.

[0057] S4. Preparation of conductive polymer-coated waste silicon composite material: 0.12 g of CMC was dispersed in 5 mL of deionized water and stirred at 60 °C for 4 h until completely dissolved, forming a homogeneous viscous solution. The solution was cooled to room temperature to obtain a CMC solution. Then, 0.02 g of APS was added, and stirring continued until dissolved to obtain an APS solution. Next, the CA-Py solution and the APS solution were mixed, followed by the addition of 0.2 g of modified nano-silicon powder particles. The mixture was reacted at 5 °C for 10 h to obtain a conductive polymer-coated photovoltaic waste silicon material.

[0058] Comparative Example 1 A method for preparing unmodified photovoltaic waste silicon material coated with a conductive polymer includes the following steps: S1. Photovoltaic waste silicon purification and particle refinement: The recovered photovoltaic crystalline silicon cutting waste is subjected to flotation, acid washing, and mechanical grinding and crushing. Flotation removes metal debris and cutting fluid residue, acid washing dissolves oxides and purifies silicon particles, and mechanical grinding and crushing is carried out to D50<100nm, so that the particle size reaches the nanoscale and obtains nano silicon powder particles.

[0059] S2, Crosslinking and Coupling of Conductive Polymer Monomers: In an ice-water bath, 0.0166 g of CA was added to 10 μL of Py, wherein the molar ratio of Py to CA was 5:3. The mixture was stirred until homogeneous to obtain a CA-Py solution.

[0060] S4. Preparation of conductive polymer-coated waste silicon composite material: 0.12 g of CMC was dispersed in 5 mL of deionized water and stirred at 60 °C for 4 h until completely dissolved, forming a homogeneous viscous solution. The solution was cooled to room temperature to obtain a CMC solution. Then, 0.02 g of APS was added, and stirring continued until dissolved to obtain an APS solution. Next, the CA-Py solution and the APS solution were mixed, followed by the addition of 0.2 g of nano-silicon powder particles. The mixture was reacted at 5 °C for 10 h to obtain a conductive polymer-coated photovoltaic waste silicon material.

[0061] Since the conductive polymer-coated photovoltaic waste silicon materials of Examples 1 to 3 have similar structures and the same performance, the conductive polymer-coated photovoltaic waste silicon material of Example 1 will be used as an example to illustrate its application in lithium-ion batteries.

[0062] Application Example 1 S1. According to the mass ratio of binder: conductive polymer-coated photovoltaic waste silicon material: acetylene black = 1:7:2, weigh 0.07g of conductive polymer-coated photovoltaic waste silicon material, 0.02g of acetylene black, and 0.01g of binder, add NMP solvent, grind evenly, then add 1-2 drops of styrene-butadiene rubber, and continue stirring until a uniform slurry is formed.

[0063] S2. Coat the copper sheet evenly with the slurry, and then cut it into a circular thin sheet with a diameter of 1.2cm as the working electrode.

[0064] S3. Finally, assemble the battery in the manual assembly box in the following order: positive electrode shell → lithium sheet (positive electrode) → separator → electrolyte → working electrode (negative electrode) → negative electrode shell. The separator is a polypropylene microporous membrane. The electrolyte is a 1.0M mixed solution of LiPF6, diethyl carbonate (DEC), and ethylene carbonate (EC) in a volume ratio of 1:1:1.

[0065] Application Example 2 The difference from Application Example 1 is as follows: the ratio of binder to conductive polymer-coated photovoltaic waste silicon material to acetylene black is 2:6:2. Weigh out 0.06g of conductive polymer-coated photovoltaic waste silicon material, 0.02g of acetylene black, and 0.02g of binder.

[0066] Figure 1 This is a SEM image of the photovoltaic waste silicon nanoparticles from Example 1 of the present invention. Figure 1 It can be seen that the modified interface (bright white area in SEM-BSE mode) and the SEI film (gray deposit) filling the pores demonstrate adaptive buffering.

[0067] Figure 2 This is the XRD pattern of the photovoltaic waste silicon nanoparticles from Example 1 of the present invention. Figure 2 It can be seen that the conductive polymer was successfully coated on the surface of the silicon particles.

[0068] Figure 3 This is the infrared spectrum of selective interface modulation of photovoltaic waste silicon according to Example 1 of the present invention. Figure 3 It can be seen that at 3400cm -1 The double peaks appearing on the left and right sides are characteristic absorptions of the NH bond in the amino group, indicating that the nitrogen-containing functional groups have successfully attached to the surface of photovoltaic waste silicon. At 1628 cm⁻¹ -1 The peak at that point represents the C=C bond vibration of the quinone structure in polyaniline, indicating that the conductive polymer was successfully coated onto the surface of photovoltaic waste silicon.

[0069] Figure 4 This is a graph showing the constant current charge-discharge cycle performance of the electrode sheet of the present invention at a current of 200 mA / g. Figure 4 It can be seen that the cycle performance is relatively stable.

[0070] Figure 5This is a graph showing the charge / discharge rate performance of the battery active material of this invention. (From...) Figure 5 It can be seen that it has good rate adaptability and can maintain the stability of the electrode structure.

[0071] In Comparative Example 1, the unmodified silicon powder combined with polypyrrole exhibited poor compatibility and dispersibility, potentially hindering electron transport and resulting in limited improvement in the composite material's conductivity. In contrast, the modified silicon powder combined with polypyrrole in the Examples effectively improved the electrode's electronic conductivity and enhanced the battery's charge-discharge performance. Uniformly dispersed silicon powder better fulfills its reinforcing role, synergistically improving the composite material's mechanical properties with polypyrrole. The strong interfacial bonding between the modified silicon powder and polypyrrole effectively transfers stress, allowing the material to better disperse and withstand loads under stress. The materials in these examples can serve as high-performance electrode materials, improving the battery's energy density and cycle stability.

[0072] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of this invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended scope of protection is intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of this invention.

[0073] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of protection of this invention and its equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a conductive polymer-coated photovoltaic waste silicon material, characterized in that, Includes the following steps: Pretreatment of photovoltaic waste silicon yields nano-silicon powder particles; Silane coupling agents are added to nano-silicon powder particles to selectively modify the interface, and organic functional group molecular chains are grafted onto the surface of nano-silicon powder particles to obtain modified nano-silicon powder particles. Using modified nano-silicon powder particles as the matrix, conductive polymer monomers are coated on them. Initiators and binders are added to induce in-situ polymerization of the conductive polymer monomers at the interface of the modified nano-silicon powder particles, forming a conductive polymer coating layer structure, thus obtaining photovoltaic waste silicon material coated with conductive polymer.

2. The method for preparing photovoltaic waste silicon material coated with conductive polymer according to claim 1, characterized in that, The molar ratio of modified nano-silicon powder particles to conductive polymer monomers is 7:1, and the conductive polymer monomers are at least one of pyrrole and aniline.

3. The method for preparing photovoltaic waste silicon material coated with conductive polymer according to claim 1, characterized in that, The mass ratio of modified nano-silicon powder particles to initiator is 1:10, and the initiator is ammonium persulfate.

4. The method for preparing photovoltaic waste silicon material coated with conductive polymer according to claim 1, characterized in that, The mass ratio of modified nano-silica powder particles to binder is 6~7:1~2, and the binder is carboxymethyl cellulose.

5. The method for preparing photovoltaic waste silicon material coated with conductive polymer according to claim 1, characterized in that, The in-situ polymerization reaction takes 8 to 12 hours and is carried out at a temperature of -5°C to 5°C.

6. The method for preparing photovoltaic waste silicon material coated with conductive polymer according to claim 1, characterized in that, The mass ratio of the silane coupling agent to the nano-silicon powder particles is 10:1, and the silane coupling agent is at least one of KH550, KH560, and KH570.

7. The method for preparing photovoltaic waste silicon material coated with conductive polymer according to claim 1, characterized in that, The selective interface modification reaction temperature is 70℃~90℃, and the reaction time is 5h~7h.

8. A conductive polymer-coated photovoltaic waste silicon material, characterized in that, It is prepared by the method described in any one of claims 1 to 7.

9. A lithium battery, characterized in that, The lithium battery is composed of a positive electrode, a negative electrode, and an electrolyte; the negative electrode is the photovoltaic waste silicon material coated with the conductive polymer as described in claim 8.

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