A method for preparing a porous silicon / carbon composite negative electrode material from photovoltaic waste glass

Abstract

The application discloses a method for preparing a porous silicon / carbon composite negative material from photovoltaic waste glass, and belongs to the technical field of waste resource recycling and utilization. The preparation method comprises the following steps: crushing the photovoltaic waste glass by ball milling to obtain photovoltaic waste glass powder; uniformly mixing the treated waste glass powder, magnesium powder and polydopamine under an inert gas, and then performing magnesium thermal reduction; performing two-step acid pickling on the composite product after the magnesium thermal reduction under low-temperature conditions; washing the acid-pickling product to neutral for multiple times, and then performing vacuum drying to obtain a silicon / carbon composite material. The reaction process is controllable, the obtained porous silicon / carbon material has low impurity content, uniform particles and good stability, and has excellent electrochemical performances such as excellent conductivity and cycle stability when applied to a lithium battery negative electrode.

Description

Technical Field

[0001] This invention relates to a method for preparing porous silicon / carbon composite anode materials using photovoltaic waste glass, belonging to the field of waste resource recycling technology. Background Technology

[0002] This research aims to recover silicon from broken waste glass using a magnesiothermal reduction technique, ultimately applying the silicon to the manufacture of lithium-ion batteries. This research will have significant environmental and economic implications, promoting the development of sustainable energy and providing new ideas for recycling waste glass from decommissioned solar panels.

[0003] In recent years, research by Chinese researchers on the recycling of silicon resources in the photovoltaic industry has mainly focused on the recycling and processing of silicon waste generated during the manufacturing of photovoltaic modules. Currently, methods for recycling silicon waste primarily revolve around crushing the silicon material, followed by purification, etching, surface modification, and mixing the processed pure silicon powder with carbon materials such as graphite and citric acid in specific proportions to obtain high-performance silicon-carbon anode materials (PSi@C) for lithium-ion batteries.

[0004] The research focus has shifted from how to recycle silicon waste generated during the production process to how to recycle silicon waste from retired photovoltaic modules. Photovoltaic waste glass accounts for over 70% of retired photovoltaic modules, and the recycling of silicon resources is the most critical and important link in the recycling process of retired photovoltaic modules.

[0005] Therefore, how to recycle photovoltaic waste glass in a low-cost and efficient manner and apply it to high-value applications has become an urgent problem for those skilled in the art. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a method for preparing porous silicon / carbon composite anode materials using photovoltaic waste glass, comprising the following steps:

[0007] (1) Remove the metal frame and junction box around the photovoltaic module to obtain the core module. Preheat the core module and then cut and separate it. The separated photovoltaic glass panel is crushed to obtain waste glass powder.

[0008] (2) The waste glass powder, magnesium powder and polydopamine obtained in step (1) are mixed and ball-milled under a protective atmosphere to obtain a uniform mixture of photovoltaic waste glass powder-magnesium powder-carbon source.

[0009] (3) Under an argon-hydrogen mixed atmosphere, the homogeneous mixture of photovoltaic waste glass powder-magnesium powder-polydopamine obtained in step (2) is subjected to a magnesium thermal reduction reaction to obtain a silicon-oxide-polydopamine composite product.

[0010] (4) The silicon-oxide-polydopamine composite product obtained in step (3) is acid-washed with hydrochloric acid.

[0011] (5) Next, the first acid washing product is placed in HF solution, and then AgNO3 solution and H2O2 are added dropwise at a rate of 0.01 ml / s for acid washing. After the addition of AgNO3 solution and H2O2 is completed, the acid washing reaction continues to obtain the second acid washing product.

[0012] (6) Finally, after washing to neutrality, filter and vacuum dry the filtered solid to obtain porous silicon / carbon composite anode material.

[0013] Preferably, in step (1), the preheating is at a temperature of 130-170°C for 40-50 minutes; the cutting and separation is done by hot knife cutting and separation at a temperature of 100-150°C.

[0014] Preferably, in step (2), the mass fraction ratio of waste glass powder, magnesium powder and polydopamine is 1:0.7:0.1 to 1:0.7:0.9; the protective gas is nitrogen or argon; the ball milling time is 6 to 8 hours; and the rotation speed is 200 to 400 r / min.

[0015] Preferably, in step (3), the magnesium thermal reduction temperature is 500-700℃, the holding time is 7-9h, and argon and hydrogen are mixed in any proportion.

[0016] Preferably, the concentration of hydrochloric acid used in step (4) is 1 to 1.5 mol / L, and the pickling time is 4 to 6 hours.

[0017] Preferably, in step (5), the concentration of AgNO3 is 0.5-1 mol / L, the concentration of H2O2 is 0.75-1.25 mol / L, the concentration of HF is 0.2-0.6 mol / L, and the volume ratio of AgNO3, H2O2 and HF is 5:1:1 to 5:1:4.

[0018] Preferably, in step (5), the dropping rate of AgNO3 and H2O2 is 0.01 ml / s, and the reaction time is 2 to 4 h.

[0019] Preferably, steps (4) and (5) are performed at 0–10°C.

[0020] Preferably, the filter paper used for filtration in step (6) has a pore size of 0.2 to 0.7 μm, the vacuum drying temperature is 60 to 80 °C, and the vacuum drying time is 3 to 5 h.

[0021] The core components described in this invention, from top to bottom, are a glass plate, an EVA film, a battery cell, another EVA film, and a TPT backsheet.

[0022] Beneficial effects of the present invention

[0023] (1) The present invention reduces silicates in photovoltaic waste glass to silicon by magnesium thermal reduction and separates them. After acid washing, the purity of Si reaches more than 99%.

[0024] (2) This invention proposes to recycle photovoltaic waste glass by magnesium thermal reduction to prepare lithium-ion battery anodes. This method utilizes the large amount of heat released during the reduction process to carbonize polydopamine in situ, forming a uniform silicon-oxide-polydopamine product, thus avoiding the problem of large heat concentration in the reaction process. It is highly efficient, environmentally friendly and economically feasible.

[0025] (3) Compared with pure silicon dioxide, the photovoltaic waste glass used in this invention contains alkali metal impurities such as calcium and sodium, so the melting point is lower, the temperature required in the magnesium thermal reduction process is lower, and less electrical energy is consumed, which is economically feasible; and the product after magnesium thermal reduction can be used to prepare lithium battery anodes, which can play a role in premagnesization and improve product performance.

[0026] (4) The present invention adopts a two-step acid washing method to remove impurities: the first step removes the oxide impurities on the surface of waste photovoltaic glass particles, and the second step removes the residual impurities inside the glass powder by acid washing and pore making. The impurity removal rate can reach 98.0-99.9%. The resulting porous silicon-carbon material has low impurity content, uniform particles, and good stability. It has excellent electrochemical properties such as conductivity and cycle stability for use in lithium battery anodes.

[0027] (5) The present invention uses photovoltaic waste glass as a reducing agent in the magnesium thermal reaction. The lithium battery anode material prepared by the present invention, after being charged and discharged at the same rate, still has a reversible capacity of 712.0 mAh / g after 312 cycles. It has better electrochemical properties such as conductivity and cycle stability than traditional magnesium thermal reduction materials.

[0028] (6) The photovoltaic waste glass used in this invention is amorphous. After magnesium thermal reduction, the silicon-oxygen bonds in the crystalline silicon are short, the stability is strong, and the conductivity is higher, which is beneficial to improving the cycle stability and conductivity of the lithium battery anode material. The photovoltaic waste glass used in this invention has a high SiO2 concentration and low impurity content, which is beneficial to improving the stability of the SEI film, reducing the occurrence of side reactions, and improving the overall performance of the battery.

[0029] (7) The photovoltaic waste glass particles used in this invention have small particle size, which makes the deposition and pore-forming effect of nano-silver particles in the magnesium thermal reduction silicon material more significant during the acid washing and etching process. This helps to improve the diffusion rate of lithium ions and the charging and discharging efficiency of the battery, and prepare nano-silver silicon-carbon composite anode materials with better performance. Attached Figure Description

[0030] Figure 1 This is a schematic flowchart of a method for preparing porous silicon / carbon composite anodes based on the recycling of photovoltaic waste glass, which is provided by the present invention.

[0031] Figure 2 This is a SEM image of the waste glass powder used in this invention.

[0032] Figure 3 This is a SEM image of waste glass powder after magnesium thermoreduction acid washing in Example 1 of the present invention.

[0033] Figure 4 The images show the XRD patterns of glass (a), after magnesium thermal reduction (b), and after acid washing (c) in Example 1 of the present invention.

[0034] Figure 5 This is a battery capacity cycle data graph from Embodiment 1 of the present invention. Detailed Implementation

[0035] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following embodiments are merely simple examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be determined by the claims.

[0036] Example 1

[0037] A method for preparing porous silicon / carbon composite anode materials using photovoltaic waste glass includes the following steps:

[0038] (1) Remove the metal frame and junction box around the photovoltaic module to obtain the core module. Place the core module on a heating platform for preheating and keep it at 150°C for 45 minutes. Heat the hot knife to 125°C and cut the glass plate and the solar cell to obtain photovoltaic waste glass plate. Crush the waste glass plate to obtain waste glass powder.

[0039] (2) The waste glass powder, magnesium powder and polydopamine obtained in step (1) are mixed in a mass fraction ratio of 1:0.7:0.5 into a ball mill jar and ball milled at 300 r / min for 7 h under a nitrogen atmosphere to obtain a uniform mixture of waste glass powder, magnesium powder and carbon source.

[0040] (3) The uniform mixture of waste glass powder, magnesium powder and carbon source obtained in step (2) is loaded into a tube furnace, the magnesium thermal reduction temperature is set to 650℃, and the furnace is kept at the temperature for 8 hours in an argon-hydrogen atmosphere. After it cools naturally to room temperature, the magnesium thermal reduction product is taken out.

[0041] (4) Place the magnesium thermal reduction reaction product obtained in step (3) and hydrochloric acid with a concentration of 1.25 mol / L in a beaker, place it on a magnetic stirrer, and perform acid washing at 5°C for 5 hours to obtain a product after one acid washing to remove impurities.

[0042] (5) The product from the first acid washing and impurity removal was placed in a 0.4 mol / L HF solution, and AgNO3 solution with a concentration of 0.75 mol / L and H2O2 with a concentration of 1 mol / L were added dropwise at a rate of 0.01 ml / s. After the AgNO3 solution and H2O2 were added, the reaction was continued at 5℃ for 3 h to obtain the product from the second acid washing.

[0043] (6) The secondary pickling product was directly washed with filter paper with a pore size of 0.6 μm until neutral, and then vacuum dried at 70°C for 4 h to obtain porous silicon / carbon composite anode material.

[0044] like Figure 3 The porous silicon / carbon composite anode material prepared as shown exhibits a porous structure on its surface, characteristic of silicon-carbon composite materials. For example... Figure 4 As shown, after magnesothermic reduction and acid washing, the impurity peaks in the XRD pattern of waste glass powder almost completely disappeared, indicating that impurities such as Mg, MgO, and SiO2 were almost completely removed.

[0045] The porous silicon / carbon composite anode material prepared in this embodiment was mixed with a conductive agent (Super P) and a binder (PVDF) at a mass ratio of 8:1:1. The mixture was then assembled into a battery in a glove box using a lithium sheet as the counter electrode. Figure 5 As can be seen, after 312 cycles of charging and discharging at 0.5C, the reversible capacity of the material reaches 712mAh / g, and the initial coulombic efficiency of the electrode can reach 88.25%.

[0046] Example 2

[0047] A method for preparing porous silicon / carbon composite anode materials using photovoltaic waste glass includes the following steps:

[0048] (1) Remove the metal frame and junction box around the photovoltaic module to obtain the core module. Place the core module on a heating platform for preheating and keep it at 130°C for 50 minutes. Heat the hot knife to 150°C and cut the glass plate and the solar cell to obtain photovoltaic waste glass plate. Crush the waste glass plate to obtain waste glass powder.

[0049] (2) The waste glass powder, magnesium powder and polydopamine obtained in step (1) are mixed in a mass fraction ratio of 1:0.7:0.1 into a ball mill jar and ball milled at 270 r / min for 7.5 h under a nitrogen atmosphere to obtain a uniform mixture of waste glass powder, magnesium powder and carbon source.

[0050] (3) The uniform mixture of waste glass powder, magnesium powder and carbon source obtained in step (2) is loaded into a tube furnace, the magnesium thermal reduction temperature is set to 500℃, and the furnace is kept at the temperature for 9 hours in an argon-hydrogen atmosphere. After it is naturally cooled to room temperature, the magnesium thermal reduction product is taken out.

[0051] (4) Place the magnesium thermal reduction reaction product obtained in step (3) and hydrochloric acid with a concentration of 1.25 mol / L in a beaker, place it on a magnetic stirrer, and perform acid washing at 10°C for 4 hours to obtain a product after one acid washing to remove impurities.

[0052] (5) The product from the first acid washing and impurity removal was placed in a 0.4 mol / L HF solution, and 0.75 mol / L AgNO3 solution and 1 mol / L H2O2 were added dropwise at a rate of 0.01 ml / s. After the AgNO3 solution and H2O2 were added, the reaction was continued at 0℃ for 4 h to obtain the product from the second acid washing.

[0053] (6) The product of secondary acid washing and impurity removal was directly washed with filter paper with a pore size of 0.7 μm until neutral, and then vacuum dried at 60°C for 3.5 h to obtain porous silicon / carbon composite anode material.

[0054] The porous silicon / carbon composite anode material prepared in this embodiment was mixed with a conductive agent (Super P) and a binder (PVDF) at a mass ratio of 8:1:1. The mixture was then assembled into a battery in a glove box with a lithium sheet as the counter electrode. After 312 cycles of charge and discharge at 0.5C, the reversible capacity of the material reached 710 mAh / g, and the initial coulombic efficiency of the electrode reached 88.01%.

[0055] Example 3

[0056] (1) Remove the metal frame and junction box around the photovoltaic module to obtain the core module. Place the core module on a heating platform for preheating and keep it at 160°C for 40 minutes. Heat the hot knife to 100°C and cut the glass plate and the solar cell to obtain photovoltaic waste glass plate. Crush the waste glass plate to obtain waste glass powder.

[0057] (2) The waste glass powder, magnesium powder and polydopamine obtained in step (1) are mixed in a mass fraction ratio of 1:0.7:0.9 into a ball mill jar and ball milled at 400 r / min for 6 h under a nitrogen atmosphere to obtain a uniform mixture of waste glass powder, magnesium powder and carbon source.

[0058] (3) The uniform mixture of waste glass powder, magnesium powder and carbon source obtained in step (2) is loaded into a tube furnace, the magnesium thermal reduction temperature is set to 670℃, and the furnace is kept at the temperature for 7.5h in an argon-hydrogen atmosphere. After it is naturally cooled to room temperature, the magnesium thermal reduction product is taken out.

[0059] (4) Place the magnesium thermal reduction reaction product obtained in step (3) and hydrochloric acid with a concentration of 1.5 mol / L in a beaker, place it on a magnetic stirrer, and perform acid washing at 0°C for 6 hours to obtain a product after one acid washing to remove impurities.

[0060] (5) The product from the first acid washing and impurity removal was placed in an HF solution with a concentration of 0.6 mol / L. Then, AgNO3 solution with a concentration of 1 mol / L and H2O2 with a concentration of 1.25 mol / L were added dropwise at a rate of 0.01 ml / s. After the AgNO3 solution and H2O2 were added, the reaction was continued at 10 °C for 2 h to obtain the product from the second acid washing.

[0061] (6) The product of secondary acid washing and impurity removal was directly washed with filter paper with a pore size of 0.2 μm until neutral, and then vacuum dried at 80°C for 3 h to obtain porous silicon / carbon composite anode material.

[0062] The porous silicon / carbon composite anode material prepared in this embodiment was mixed with a conductive agent (Super P) and a binder (PVDF) at a mass ratio of 8:1:1. The mixture was then assembled into a battery in a glove box with a lithium sheet as the counter electrode. After 312 cycles of charge and discharge at 0.5C, the reversible capacity of the material reached 707 mAh / g, and the initial coulombic efficiency of the electrode reached 87.16%.

[0063] Example 4

[0064] (1) Remove the metal frame and junction box around the photovoltaic module to obtain the core module. Place the core module on a heating platform for preheating and keep it at 170°C for 40 minutes. Heat the hot knife to 110°C and cut the glass plate and the solar cell to obtain photovoltaic waste glass plate. Crush the waste glass plate to obtain waste glass powder.

[0065] (2) The waste glass powder, magnesium powder and polydopamine obtained in step (1) are mixed in a mass fraction ratio of 1:0.7:0.6 into a ball mill jar and ball milled at 200 r / min for 8 h under an argon atmosphere to obtain a uniform mixture of waste glass powder, magnesium powder and carbon source.

[0066] (3) The uniform mixture of waste glass powder, magnesium powder and carbon source obtained in step (2) is loaded into a tube furnace, the magnesium thermal reduction temperature is set to 700℃, and the furnace is kept at the temperature for 7 hours in an argon-hydrogen atmosphere. After it cools naturally to room temperature, the magnesium thermal reduction product is taken out.

[0067] (4) Place the magnesium thermal reduction reaction product obtained in step (3) and hydrochloric acid with a concentration of 1 mol / L in a beaker, place it on a magnetic stirrer, and perform acid washing at 5°C for 4.5 h to obtain a product after one acid washing to remove impurities.

[0068] (5) The product from the first acid washing and impurity removal was placed in a 0.2 mol / L HF solution, and 0.5 mol / L AgNO3 solution and 0.75 mol / L H2O2 were added dropwise at a rate of 0.01 ml / s. After the AgNO3 solution and H2O2 were added, the reaction was continued at 5 °C for 3 h to obtain the product from the second acid washing.

[0069] (6) The product of secondary acid washing and impurity removal was directly washed with filter paper with a pore size of 0.6 μm until neutral, and then vacuum dried at 60°C for 5 h to obtain porous silicon / carbon composite anode material.

[0070] The porous silicon / carbon composite anode material prepared in this embodiment was mixed with a conductive agent (Super P) and a binder (PVDF) at a mass ratio of 8:1:1. The mixture was then assembled into a battery in a glove box with a lithium sheet as the counter electrode. After 312 cycles of charge and discharge at 0.5C, the reversible capacity of the material reached 709 mAh / g, and the initial coulombic efficiency of the electrode reached 87.55%.

[0071] Comparative Example 1

[0072] For comparison, the preparation method of this embodiment is the same as that of Example 1, except that polydopamine is replaced with graphite. The reason why the material prepared in this embodiment is not as good as that of Example 1 is that polydopamine has better conductivity, which can improve the conductivity of silicon-carbon anode material, accelerate the electron transport rate, and further optimize the charge and discharge performance of the battery. Moreover, through the cross-linking effect of polydopamine, a three-dimensional network structure can be formed, which is beneficial to improving the structural stability between silicon particles and promoting the rapid transport of lithium ions, thus greatly improving the electrochemical performance of silicon-carbon anode material.

[0073] Comparative Example 2

[0074] In comparison, the preparation method of this embodiment is the same as that of Example 1, except that the second acid washing in step (5) is not performed. The reason why the material prepared in this embodiment is not as good as that in Example 1 is that the content of impurities such as Al and B in the first acid washing product is relatively high, which leads to a decrease in the stability of the SEI film during battery charging and discharging, a decrease in the conductivity of the silicon-carbon anode material, and a reduction in the electrochemical performance of the battery. In addition, compared with the silicon-carbon material (Si@PDA) prepared by the first acid washing product, the second acid washing can simultaneously achieve the "etching + pore formation" of nano-silver particles on the surface of silicon. The prepared silicon-carbon composite anode material (PSi / Ag@PDA) has a porous structure, which inhibits the expansion of silicon material during battery charging and discharging. The nano-silver particles deposited in the pores can also improve the conductivity of the material, thus greatly improving the electrochemical performance.

Claims

1. A method for preparing porous silicon / carbon composite anode materials using photovoltaic waste glass, characterized in that: Includes the following steps: (1) Remove the metal frame and junction box around the photovoltaic module to obtain the core module. Preheat the core module and then cut and separate it. The separated photovoltaic waste glass plate is crushed to obtain waste glass powder. (2) The waste glass powder, magnesium powder and polydopamine obtained in step (1) are ball-milled under a protective atmosphere to obtain a uniform mixture of photovoltaic waste glass powder-magnesium powder-polydopamine. (3) Under an argon-hydrogen mixed atmosphere, the homogeneous mixture of photovoltaic waste glass powder-magnesium powder-polydopamine obtained in step (2) is subjected to a magnesium thermal reduction reaction to obtain a silicon-oxide-polydopamine composite product. (4) The silicon-oxide-polydopamine composite product obtained in step (3) is acid-washed with hydrochloric acid to obtain the first acid-washed product; (5) Next, the first acid washing product is placed in HF solution, and AgNO3 solution and H2O2 are added dropwise for acid washing. After the AgNO3 solution and H2O2 are added, the reaction continues to obtain the second acid washing product. (6) Wash the second acid washing product with filter paper until neutral, and vacuum dry the filtered solid to obtain a porous silicon / carbon composite anode material; The concentration of hydrochloric acid used in step (4) is 1~1.5mol / L, and the pickling time is 4~6h; In step (5), the concentration of AgNO3 is 0.5~1mol / L, the concentration of H2O2 is 0.75~1.25mol / L, the concentration of HF is 0.2~0.6mol / L, and the volume ratio of AgNO3, H2O2 and HF is 5:1:1~5:1:4; In step (5), the dropping rate of AgNO3 and H2O2 is 0.01 ml / s, and the reaction time is 2-4 h.

2. The method for preparing porous silicon / carbon composite anode material using photovoltaic waste glass according to claim 1, characterized in that: In step (1), the preheating is at a temperature of 130~170℃ for 40~50min; the cutting and separation is hot knife cutting and separation at a temperature of 100~150℃.

3. The method for preparing porous silicon / carbon composite anode material using photovoltaic waste glass according to claim 1, characterized in that: In step (2), the mass fraction ratio of waste glass powder, magnesium powder and polydopamine is 1:0.7:0.1~1:0.7:0.9 respectively; the protective gas is nitrogen or argon, the ball milling time is 6~8h, and the rotation speed is 200~400r / min.

4. The method for preparing porous silicon / carbon composite anode material using photovoltaic waste glass according to claim 1, characterized in that: In step (3), the magnesium thermal reduction temperature is 500~700℃ and the holding time is 7~9h.

5. The method for preparing porous silicon / carbon composite anode material using photovoltaic waste glass according to claim 1, characterized in that: Steps (4) and (5) are performed at 0~10℃.

6. The method for preparing porous silicon / carbon composite anode material using photovoltaic waste glass according to claim 1, characterized in that: Step (6) The filter paper used for filtration has a pore size of 0.2~0.7um, the vacuum drying temperature is 60~80℃, and the vacuum drying time is 3~5h.

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