Silicon-based negative pole piece and preparation method thereof

Abstract

The invention discloses a silicon-based negative pole piece and a preparation method thereof, and relates to the technical field of silicon-based pole pieces. The preparation method comprises the following steps: 1, carrying out oxidation treatment and reduction treatment on black phosphorus and graphene oxide together to obtain a black phosphorus / graphene composite material with a pore structure; 2, the black phosphorus / graphene composite material and nanometer silicon powder are pretreated, then the nanometer silicon powder is coated with the black phosphorus / graphene composite material, and a black phosphorus / graphene nanometer silicon powder material is obtained; step 3, adding the black phosphorus / graphene nanometer silicon powder material into a sodium polyacrylate solution, carrying out stirring reaction, and carrying out freeze drying, grinding and carbonization treatment to obtain a graphite / black phosphorus / graphene nanometer silicon powder material; 4, uniformly stirring and mixing the graphite-black phosphorus / graphene-nanometer silicon powder material, a conductive agent and a binder, and rolling to obtain an electrode film; and attaching the electrode films to the two surfaces of the aluminum foil, and rolling to obtain the silicon-based negative pole piece.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon-based pole pieces, and in particular to a silicon-based negative pole piece and a preparation method thereof. Background Art

[0002] With the rapid growth in demand for lithium-ion batteries in electric vehicles, portable electronic devices, and other fields, the development of anode materials with high energy density and long cycle life has become a research hotspot. Silicon-based anodes have attracted much attention due to their theoretical specific capacity of up to 4200 mAh / g (far exceeding the 372 mAh / g of graphite), but their industrialization still faces two core challenges: the volume expansion of silicon (300-400%) during charge and discharge, which leads to pulverization and failure of the electrode structure; and the poor intrinsic conductivity of silicon, which leads to increased polarization and capacity decay. Traditional solutions such as nano-silicon particles (to reduce expansion stress) and carbon coating (to improve conductivity) can partially alleviate this problem, but a single modification strategy cannot balance mechanical support, ion transport, and interface stability. For example, pure carbon-coated nano-silicon will still fail due to delamination of the silicon-carbon interface during long-term cycling; and while graphene-composite silicon-based materials can form a conductive network, they lack the ability to dynamically buffer silicon volume expansion.

[0003] In recent years, multi-component composites and structural design have become key areas for overcoming bottlenecks. Black phosphorus, due to its layered structure, high carrier mobility, and flexibility, has been explored as a mechanical buffer layer and conductivity-enhancing phase for silicon-based anodes. The porous graphene network formed by the reduction of graphene oxide provides a high specific surface area and ion transport channels.

[0004] Based on this, the present invention proposes a method for preparing a silicon-based negative electrode sheet synergistically reinforced with black phosphorus and graphene oxide. This method can mitigate silicon volume expansion and improve ion / electron transport efficiency, potentially breaking through the cycle life and energy density bottlenecks of silicon-based negative electrodes. This provides new insights for the development of next-generation high-energy-density lithium-ion batteries, which is of great significance. Summary of the Invention

[0005] The object of the present invention is to provide a silicon-based negative electrode plate and a preparation method thereof to solve the problems raised in the above background technology.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] A method for preparing a silicon-based negative electrode plate comprises the following steps:

[0008] Step 1: performing oxidation and reduction treatment on black phosphorus and graphene oxide to obtain a black phosphorus / graphene composite material with a porous structure;

[0009] Step 2: Pre-treating the black phosphorus / graphene composite material and nano-silicon powder respectively, and then coating the nano-silicon powder with the black phosphorus / graphene composite material to obtain a black phosphorus / graphene@nano-silicon powder material;

[0010] Step 3: Adding the black phosphorus / graphene@nano-silicon powder material to the sodium polyacrylate solution, stirring and reacting for a period of time, and then freeze-drying, grinding, and carbonizing to obtain the graphite@black phosphorus / graphene@nano-silicon powder material;

[0011] Step 4: Mix the graphite@black phosphorus / graphene@nano-silicon powder material, conductive agent, and binder evenly, and roll-press to obtain an electrode film; attach the electrode film to both sides of the aluminum foil, and then roll-press to obtain a silicon-based negative electrode sheet.

[0012] Furthermore, the preparation method of the black phosphorus / graphene oxide composite material is as follows: (1) adding black phosphorus and graphene oxide to N-methylpyrrolidone, ultrasonically dispersing for 1 to 6 hours, and obtaining a black phosphorus / graphene oxide dispersion; (2) heating the black phosphorus / graphene oxide dispersion to 50 to 70° C., adjusting its pH to 2 to 4, and then adding 20 to 40 wt% hydrogen peroxide aqueous solution thereto, stirring and reacting for 1 to 6 hours to complete oxidation treatment, and after naturally cooling to room temperature, filtering, washing, and drying to obtain a black phosphorus / graphene oxide oxidation product; (3) heating a 50 to 70 wt% hydrazine hydrate aqueous solution to 80 to 100° C., adjusting its pH to 8 to 10, and then adding the black phosphorus / graphene oxide oxidation product thereto, stirring and reacting for 12 to 48 hours to complete reduction treatment, and after naturally cooling to room temperature, filtering, washing, and drying to obtain a black phosphorus / graphene oxide composite material.

[0013] Furthermore, in the black phosphorus / graphene oxide dispersion, the concentration of black phosphorus is 1 to 5 mg / L, and the concentration of graphene oxide is 1 to 5 mg / L.

[0014] Furthermore, the volume ratio of the black phosphorus / graphene oxide dispersion to the hydrogen peroxide aqueous solution is 10:(1-2).

[0015] Furthermore, the ratio of the hydrazine hydrate aqueous solution to the black phosphorus / graphene oxide oxidation product is 10 mL: (1-2) g.

[0016] Furthermore, the preparation method of the black phosphorus / graphene@nano-silicon powder material is as follows: (1) under the protection of inert gas, the black phosphorus / graphene composite material and the surfactant are added to isopropyl alcohol, ultrasonically dispersed for 30 to 60 minutes, filtered, washed, and dried to obtain a pretreated black phosphorus / graphene composite material; (2) the nano-silicon powder is added to a 10 to 20 wt% hydrogen peroxide aqueous solution, ultrasonically dispersed for 30 to 60 minutes, filtered, washed, and dried to obtain a pretreated nano-silicon powder; (3) the pretreated black phosphorus / graphene composite material is added to deionized water, ultrasonically dispersed for 30 to 60 minutes, and then the pretreated nano-silicon powder is added thereto, stirred for reaction for 1 to 6 hours, filtered, washed, and dried to obtain a black phosphorus / graphene@nano-silicon powder material.

[0017] Furthermore, the surfactant is a cationic surfactant, and the added amount is 1 to 2% of the mass of the black phosphorus / graphene composite material.

[0018] Furthermore, the ratio of the nano-silicon powder to the hydrogen peroxide aqueous solution is (1-2) g:10 mL.

[0019] Furthermore, the mass ratio of the pretreated black phosphorus / graphene composite material to the pretreated nano-silicon powder is (0.1-0.3):1.

[0020] Furthermore, the preparation method of the graphite @ black phosphorus / graphene @ nano silicon powder material is as follows: sodium polyacrylate is added to deionized water, ultrasonically dispersed for 30 to 60 minutes, then black phosphorus / graphene @ nano silicon powder material is added thereto, stirred and reacted for 1 to 6 hours, and freeze-dried, ground, and carbonized to obtain the graphite @ black phosphorus / graphene @ nano silicon powder material.

[0021] Furthermore, the mass ratio of the sodium polyacrylate and the black phosphorus / graphene@nano-silicon powder material is 2:1.

[0022] Furthermore, the parameters of the carbonization treatment are: under the protection of inert gas, heating to 580-720° C. at a heating rate of 5° C. / min, and keeping warm for 1-3 hours.

[0023] Furthermore, the mass ratio of the graphite@black phosphorus / graphene@nano-silicon powder material, the conductive agent, and the binder is (87-90):(5-7):(3-6).

[0024] Furthermore, the temperature of the rolling is 150-180°C.

[0025] Furthermore, the thickness of the electrode film is 150 to 250 μm.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) In the present invention, by controlling the reaction conditions such as the concentration of hydrogen peroxide, the concentration of hydrazine hydrate, the reaction temperature, the reaction time, and the pH value, black phosphorus and graphene oxide are oxidized to form pores, so that they have a controllable, multi-scale, dense pore structure. On the one hand, these pore structures can provide space for the subsequent volume expansion of silicon, reducing the damage to the electrode structure caused by expansion stress. On the other hand, the dense pore structure forms a continuous conductive network structure, effectively improving the electron transfer rate, and comprehensively enhancing the volume expansion rate and electrochemical performance of the silicon-based negative electrode.

[0028] (2) In the present invention, the black phosphorus / graphene composite material and nano-silicon powder are further pretreated, which effectively avoids the agglomeration problem that may occur during the coating process, and makes the coating of the black phosphorus / graphene composite material on the nano-silicon powder and the coating of the graphite on the black phosphorus / graphene@nano-silicon powder material become tighter, and the interface between the layers is stable, thereby ensuring the stability of the silicon-based electrode.

[0029] (3) Since the layers are tightly packed together, the volume expansion of silicon is further limited while the electron transfer rate is guaranteed, thereby enhancing the conductivity of the electrode material. At the same time, direct contact between silicon and the electrolyte is greatly avoided, thus reducing side reactions.

[0030] In summary, the present invention comprehensively prepares a silicon-based negative electrode sheet that can effectively inhibit silicon volume expansion and has excellent electrochemical performance. DETAILED DESCRIPTION

[0031] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0032] It should be noted that the following parts are calculated by weight, and the purchasers of all raw materials involved in the present invention include, without any special restrictions, the following examples:

[0033] In the following examples, black phosphorus, item number: B196539, graphene oxide, item number: G139803, with a sheet diameter of 0.5 to 3 μm and a thickness of 0.55 to 1.2 nm, hydrazine hydrate, with a purity of 97%, and sodium polyacrylate, with an average molecular weight of 4 to 5 million, were all purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0034] Nano-silicon powder with a purity of 99.99%, product number: M24893, particle size 50 nm, was purchased from Shanghai Myrrel Biochemical Technology Co., Ltd.; the remaining raw materials were purchased from the market.

[0035] Example 1: A method for preparing a silicon-based negative electrode plate:

[0036] Step 1: Preparation of black phosphorus / graphene composite material: (1) Add black phosphorus and graphene oxide into a ball mill, grind them evenly, add them into N-methylpyrrolidone, and ultrasonically disperse them for 4 hours to obtain a black phosphorus / graphene oxide dispersion, wherein the concentration of black phosphorus is 3 mg / L and the concentration of graphene oxide is 3 mg / L; (2) Heat the black phosphorus / graphene oxide dispersion to 60°C, adjust its pH to 3, and then add 30wt% hydrogen peroxide aqueous solution thereto, stir and react for 4 hours to complete the oxidation treatment, wait for it to cool naturally to room temperature, filter, wash, Drying to obtain a black phosphorus / graphene oxide oxidation product, wherein the volume ratio of the black phosphorus / graphene oxide dispersion to the hydrogen peroxide aqueous solution is 10:1.5; (3) heating a 60wt% hydrazine hydrate aqueous solution to 90°C, adjusting its pH to 9, and then adding the black phosphorus / graphene oxide oxidation product thereto, stirring and reacting for 36 hours to complete the reduction treatment, and after naturally cooling to room temperature, filtering, washing, and drying to obtain a black phosphorus / graphene composite material, wherein the ratio of the hydrazine hydrate aqueous solution to the black phosphorus / graphene oxide oxidation product is 10mL:1.5g;

[0037] Step 2: Preparation of black phosphorus / graphene@nano-silicon powder material: (1) Under nitrogen protection, black phosphorus / graphene composite material and hexadecyltrimethylammonium bromide are added to isopropanol, ultrasonically dispersed for 45 minutes, filtered, washed and dried to obtain a pretreated black phosphorus / graphene composite material, wherein the amount of hexadecyltrimethylammonium bromide added is 1.5% of the mass of the black phosphorus / graphene composite material; (2) Nano-silicon powder is added to a 15wt% hydrogen peroxide aqueous solution, ultrasonically dispersed for 45 minutes, filtered, washed and dried to obtain pretreated nano-silicon powder, wherein the ratio of nano-silicon powder to hydrogen peroxide aqueous solution is 1.5g:10mL; (3) The pretreated black phosphorus / graphene composite material is added to deionized water, ultrasonically dispersed for 45 minutes, and then the pretreated nano-silicon powder is added thereto, stirred for reaction for 4 hours, filtered, washed and dried to obtain a black phosphorus / graphene@nano-silicon powder material, wherein the mass ratio of the pretreated black phosphorus / graphene composite material to the pretreated nano-silicon powder is 0.2:1;

[0038] Step 3: Preparation of graphite @ black phosphorus / graphene @ nano-silicon powder material: Sodium polyacrylate was added to deionized water and ultrasonically dispersed for 45 minutes. Black phosphorus / graphene @ nano-silicon powder material was then added thereto and stirred for reaction for 4 hours. The mixture was freeze-dried, ground, and carbonized (under nitrogen protection, the temperature was increased to 650°C at a heating rate of 5°C / min and kept warm for 2 hours) to obtain graphite @ black phosphorus / graphene @ nano-silicon powder material, wherein the mass ratio of sodium polyacrylate to black phosphorus / graphene @ nano-silicon powder material was 2:1;

[0039] Step 4: Add graphite@black phosphorus / graphene@nanosilicon powder material, conductive carbon black and polytetrafluoroethylene in a mass ratio of 90:6:4 into a blender, stir and mix evenly to obtain a mixture; then add it to a roller press and roll it at 160°C to obtain a 200μm thick electrode film; attach the electrode film to both sides of a 12μm thick aluminum foil, and then roll it at 160°C to obtain a silicon-based negative electrode sheet.

[0040] Example 2: A method for preparing a silicon-based negative electrode plate:

[0041] Step 1: Preparation of black phosphorus / graphene composite material: (1) Add black phosphorus and graphene oxide into a ball mill, grind them evenly, add them into N-methylpyrrolidone, and ultrasonically disperse them for 1 hour to obtain a black phosphorus / graphene oxide dispersion, wherein the concentration of black phosphorus is 1 mg / L and the concentration of graphene oxide is 1 mg / L; (2) Heat the black phosphorus / graphene oxide dispersion to 50°C, adjust its pH to 2, and then add 20 wt% hydrogen peroxide aqueous solution thereto, stir and react for 1 hour to complete the oxidation treatment, wait for it to cool naturally to room temperature, filter, wash and (3) heating a 50 wt % hydrazine hydrate aqueous solution to 80° C., adjusting its pH to 8, and then adding the black phosphorus / graphene oxide oxidation product thereto, stirring and reacting for 12 h to complete the reduction treatment, and after naturally cooling to room temperature, filtering, washing, and drying to obtain a black phosphorus / graphene composite material, wherein the ratio of the hydrazine hydrate aqueous solution to the black phosphorus / graphene oxide oxidation product is 10 mL:1 g;

[0042] Step 2: Preparation of black phosphorus / graphene@nano-silicon powder material: (1) Under nitrogen protection, black phosphorus / graphene composite material and hexadecyltrimethylammonium bromide are added to isopropanol, ultrasonically dispersed for 30 minutes, filtered, washed and dried to obtain a pretreated black phosphorus / graphene composite material, wherein the amount of hexadecyltrimethylammonium bromide added is 1% of the mass of the black phosphorus / graphene composite material; (2) Nano-silicon powder is added to a 10wt% hydrogen peroxide aqueous solution, ultrasonically dispersed for 30 minutes, filtered, washed and dried to obtain pretreated nano-silicon powder, wherein the ratio of nano-silicon powder to hydrogen peroxide aqueous solution is 2g:10mL; (3) The pretreated black phosphorus / graphene composite material is added to deionized water, ultrasonically dispersed for 30 minutes, and then the pretreated nano-silicon powder is added thereto, stirred for reaction for 1 hour, filtered, washed and dried to obtain a black phosphorus / graphene@nano-silicon powder material, wherein the mass ratio of the pretreated black phosphorus / graphene composite material to the pretreated nano-silicon powder is 0.1:1;

[0043] Step 3: Preparation of graphite @ black phosphorus / graphene @ nano silicon powder material: Sodium polyacrylate was added to deionized water and ultrasonically dispersed for 30 minutes, and then black phosphorus / graphene @ nano silicon powder material was added thereto, stirred and reacted for 1 hour, and freeze-dried, ground, and carbonized (under nitrogen gas protection, heating rate of 5 ° C / min, heating to 580 ° C, and keeping warm for 1 hour) to obtain graphite @ black phosphorus / graphene @ nano silicon powder material, wherein the mass ratio of sodium polyacrylate to black phosphorus / graphene @ nano silicon powder material is 2:1;

[0044] Step 4: Add graphite@black phosphorus / graphene@nanosilicon powder material, conductive carbon black and polytetrafluoroethylene in a mass ratio of 90:6:4 into a blender, stir and mix evenly to obtain a mixture; then add it to a roller press and roll it at 160°C to obtain a 200μm thick electrode film; attach the electrode film to both sides of a 12μm thick aluminum foil, and then roll it at 160°C to obtain a silicon-based negative electrode sheet.

[0045] Example 3: A method for preparing a silicon-based negative electrode plate:

[0046] Step 1: Preparation of black phosphorus / graphene composite material: (1) Add black phosphorus and graphene oxide into a ball mill, grind them evenly, add them into N-methylpyrrolidone, and ultrasonically disperse them for 6 hours to obtain a black phosphorus / graphene oxide dispersion, wherein the concentration of black phosphorus is 5 mg / L and the concentration of graphene oxide is 5 mg / L; (2) Heat the black phosphorus / graphene oxide dispersion to 70°C, adjust its pH to 4, and then add 40 wt% hydrogen peroxide aqueous solution thereto, stir and react for 6 hours to complete the oxidation treatment, wait for it to cool naturally to room temperature, filter, wash and , drying to obtain a black phosphorus / graphene oxide oxidation product, wherein the volume ratio of the black phosphorus / graphene oxide dispersion and the hydrogen peroxide aqueous solution is 10:2; (3) heating a 70wt% hydrazine hydrate aqueous solution to 100°C, adjusting its pH to 10, and then adding the black phosphorus / graphene oxide oxidation product thereto, stirring and reacting for 48h to complete the reduction treatment, and after naturally cooling to room temperature, filtering, washing, and drying to obtain a black phosphorus / graphene composite material, wherein the ratio of the hydrazine hydrate aqueous solution to the black phosphorus / graphene oxide oxidation product is 10mL:2g;

[0047] Step 2: Preparation of black phosphorus / graphene@nano-silicon powder material: (1) Under nitrogen protection, black phosphorus / graphene composite material and hexadecyltrimethylammonium bromide are added to isopropanol, ultrasonically dispersed for 60 minutes, filtered, washed and dried to obtain a pretreated black phosphorus / graphene composite material, wherein the amount of hexadecyltrimethylammonium bromide added is 2% of the mass of the black phosphorus / graphene composite material; (2) Nano-silicon powder is added to a 20wt% hydrogen peroxide aqueous solution, ultrasonically dispersed for 60 minutes, filtered, washed and dried to obtain pretreated nano-silicon powder, wherein the ratio of nano-silicon powder to hydrogen peroxide aqueous solution is 1g:10mL; (3) The pretreated black phosphorus / graphene composite material is added to deionized water, ultrasonically dispersed for 60 minutes, and then the pretreated nano-silicon powder is added thereto, stirred for reaction for 6 hours, filtered, washed and dried to obtain a black phosphorus / graphene@nano-silicon powder material, wherein the mass ratio of the pretreated black phosphorus / graphene composite material to the pretreated nano-silicon powder is 0.3:1;

[0048] Step 3: Preparation of graphite @ black phosphorus / graphene @ nano silicon powder material: Sodium polyacrylate was added to deionized water and ultrasonically dispersed for 60 minutes, and then black phosphorus / graphene @ nano silicon powder material was added thereto, stirred and reacted for 6 hours, and freeze-dried, ground, and carbonized (under nitrogen gas protection, heating rate of 5 ° C / min, heating to 720 ° C, and keeping warm for 3 hours) to obtain graphite @ black phosphorus / graphene @ nano silicon powder material, wherein the mass ratio of sodium polyacrylate to black phosphorus / graphene @ nano silicon powder material is 2:1;

[0049] Step 4: Add graphite@black phosphorus / graphene@nanosilicon powder material, conductive carbon black and polytetrafluoroethylene in a mass ratio of 90:6:4 into a blender, stir and mix evenly to obtain a mixture; then add it to a roller press and roll it at 160°C to obtain a 200μm thick electrode film; attach the electrode film to both sides of a 12μm thick aluminum foil, and then roll it at 160°C to obtain a silicon-based negative electrode sheet.

[0050] The following control experiments are set up based on Example 1, specifically comparative examples 1 to 4, as shown below:

[0051] Comparative Example 1: Comparative Example 1 is based on Example 1, with the following adjustments: black phosphorus and graphene oxide are not subjected to oxidation and reduction treatments, and other processes remain unchanged, specifically:

[0052] A method for preparing a silicon-based negative electrode plate:

[0053] Step 1: Preparation of black phosphorus / graphene composite material: (1) adding black phosphorus and graphene oxide into a ball mill, grinding them uniformly, adding them into N-methylpyrrolidone, ultrasonically dispersing them for 4 h, filtering, washing, and drying to obtain a black phosphorus / graphene composite material, wherein the mass ratio of the two is 1:1;

[0054] Step 2: Preparation of black phosphorus / graphene@nano-silicon powder material: (1) Under nitrogen protection, black phosphorus / graphene composite material and hexadecyltrimethylammonium bromide are added to isopropanol, ultrasonically dispersed for 45 minutes, filtered, washed and dried to obtain a pretreated black phosphorus / graphene composite material, wherein the amount of hexadecyltrimethylammonium bromide added is 1.5% of the mass of the black phosphorus / graphene composite material; (2) Nano-silicon powder is added to a 15wt% hydrogen peroxide aqueous solution, ultrasonically dispersed for 45 minutes, filtered, washed and dried to obtain pretreated nano-silicon powder, wherein the ratio of nano-silicon powder to hydrogen peroxide aqueous solution is 1.5g:10mL; (3) The pretreated black phosphorus / graphene composite material is added to deionized water, ultrasonically dispersed for 45 minutes, and then the pretreated nano-silicon powder is added thereto, stirred for reaction for 4 hours, filtered, washed and dried to obtain a black phosphorus / graphene@nano-silicon powder material, wherein the mass ratio of the pretreated black phosphorus / graphene composite material to the pretreated nano-silicon powder is 0.2:1;

[0055] Step 3: Preparation of graphite @ black phosphorus / graphene @ nano-silicon powder material: Sodium polyacrylate was added to deionized water and ultrasonically dispersed for 45 minutes. Black phosphorus / graphene @ nano-silicon powder material was then added thereto and stirred for reaction for 4 hours. The mixture was freeze-dried, ground, and carbonized (under nitrogen protection, the temperature was increased to 650°C at a heating rate of 5°C / min and kept warm for 2 hours) to obtain graphite @ black phosphorus / graphene @ nano-silicon powder material, wherein the mass ratio of sodium polyacrylate to black phosphorus / graphene @ nano-silicon powder material was 2:1;

[0056] Step 4: Add graphite@black phosphorus / graphene@nanosilicon powder material, conductive carbon black and polytetrafluoroethylene in a mass ratio of 90:6:4 into a blender, stir and mix evenly to obtain a mixture; then add it to a roller press and roll it at 160°C to obtain a 200μm thick electrode film; attach the electrode film to both sides of a 12μm thick aluminum foil, and then roll it at 160°C to obtain a silicon-based negative electrode sheet.

[0057] Comparative Example 2: Comparative Example 2 is based on Example 1, with the following adjustments: no pretreatment is performed on the black phosphorus / graphene composite material and nano-silicon powder, and other processes remain unchanged, specifically:

[0058] A method for preparing a silicon-based negative electrode plate:

[0059] Step 1: Preparation of black phosphorus / graphene composite material: (1) Add black phosphorus and graphene oxide into a ball mill, grind them evenly, add them into N-methylpyrrolidone, and ultrasonically disperse them for 4 hours to obtain a black phosphorus / graphene oxide dispersion, wherein the concentration of black phosphorus is 3 mg / L and the concentration of graphene oxide is 3 mg / L; (2) Heat the black phosphorus / graphene oxide dispersion to 60°C, adjust its pH to 3, and then add 30wt% hydrogen peroxide aqueous solution thereto, stir and react for 4 hours to complete the oxidation treatment, wait for it to cool naturally to room temperature, filter, wash, Drying to obtain a black phosphorus / graphene oxide oxidation product, wherein the volume ratio of the black phosphorus / graphene oxide dispersion to the hydrogen peroxide aqueous solution is 10:1.5; (3) heating a 60wt% hydrazine hydrate aqueous solution to 90°C, adjusting its pH to 9, and then adding the black phosphorus / graphene oxide oxidation product thereto, stirring and reacting for 36 hours to complete the reduction treatment, and after naturally cooling to room temperature, filtering, washing, and drying to obtain a black phosphorus / graphene composite material, wherein the ratio of the hydrazine hydrate aqueous solution to the black phosphorus / graphene oxide oxidation product is 10mL:1.5g;

[0060] Step 2: Preparation of black phosphorus / graphene@nanosilicon powder material: Add the black phosphorus / graphene composite material to deionized water, ultrasonically disperse for 45 minutes, then add nanosilicon powder, stir and react for 4 hours, filter, wash and dry to obtain the black phosphorus / graphene@nanosilicon powder material, wherein the mass ratio of the black phosphorus / graphene composite material to the nanosilicon powder is 0.2:1;

[0061] Step 3: Preparation of graphite @ black phosphorus / graphene @ nano-silicon powder material: Sodium polyacrylate was added to deionized water and ultrasonically dispersed for 45 minutes. Black phosphorus / graphene @ nano-silicon powder material was then added thereto and stirred for reaction for 4 hours. The mixture was freeze-dried, ground, and carbonized (under nitrogen protection, the temperature was increased to 650°C at a heating rate of 5°C / min and kept warm for 2 hours) to obtain graphite @ black phosphorus / graphene @ nano-silicon powder material, wherein the mass ratio of sodium polyacrylate to black phosphorus / graphene @ nano-silicon powder material was 2:1;

[0062] Step 4: Add graphite@black phosphorus / graphene@nanosilicon powder material, conductive carbon black and polytetrafluoroethylene in a mass ratio of 90:6:4 into a blender, stir and mix evenly to obtain a mixture; then add it to a roller press and roll it at 160°C to obtain a 200μm thick electrode film; attach the electrode film to both sides of a 12μm thick aluminum foil, and then roll it at 160°C to obtain a silicon-based negative electrode sheet.

[0063] Comparative Example 3: Comparative Example 3 is based on Example 1, with the following adjustments: sodium polyacrylate is directly used to coat the nano-silicon powder, and other processes remain unchanged, specifically:

[0064] A method for preparing a silicon-based negative electrode plate:

[0065] Step 1: Preparation of graphite@nano-silicon powder material: Sodium polyacrylate was added to deionized water and ultrasonically dispersed for 45 minutes. Then, nano-silicon powder material was added thereto and stirred for reaction for 4 hours. The mixture was freeze-dried, ground, and carbonized (under nitrogen protection, the temperature was increased to 650°C at a heating rate of 5°C / min and kept warm for 2 hours) to obtain graphite@nano-silicon powder material, wherein the mass ratio of sodium polyacrylate to nano-silicon powder material was 2:1;

[0066] Step 4: Add graphite@nano silicon powder material, conductive carbon black and polytetrafluoroethylene in a mass ratio of 90:6:4 into a blender, stir and mix evenly to obtain a mixture; then add it to a roller press and roll it at 160°C to obtain a 200μm thick electrode film; attach the electrode film to both sides of a 12μm thick aluminum foil, and then roll it at 160°C to obtain a silicon-based negative electrode sheet.

[0067] Comparative Example 4: Comparative Example 4 is based on Example 1, with the following adjustments: no black phosphorus is added, and other processes remain unchanged, specifically:

[0068] A method for preparing a silicon-based negative electrode plate:

[0069] Step 1: Preparation of graphene oxide reduction product: (1) Add graphene oxide into a ball mill, grind it evenly, add it into N-methylpyrrolidone, and ultrasonically disperse it for 4 hours to obtain a graphene oxide dispersion with a concentration of 3 mg / L; (2) Heat the graphene oxide dispersion to 60°C, adjust its pH to 3, and then add 30wt% hydrogen peroxide aqueous solution thereto, stir and react for 4 hours to complete the oxidation treatment, wait for it to cool naturally to room temperature, filter, wash, and dry to obtain graphene oxide. (3) heating a 60 wt % hydrazine hydrate aqueous solution to 90° C., adjusting its pH to 9, and then adding the graphene oxide oxidation product thereto, stirring and reacting for 36 hours to complete the reduction treatment, and after naturally cooling to room temperature, filtering, washing, and drying to obtain a graphene oxide reduction product, wherein the ratio of the hydrazine hydrate aqueous solution to the graphene oxide oxidation product is 10 mL:1.5 g;

[0070] Step 2: Preparation of graphene@nanosilicon powder material: (1) Under nitrogen protection, graphene oxide reduction product and hexadecyltrimethylammonium bromide are added to isopropanol, ultrasonically dispersed for 45 minutes, filtered, washed, and dried to obtain pretreated graphene, wherein the amount of hexadecyltrimethylammonium bromide added is 1.5% of the mass of the graphene oxide reduction product; (2) Nanosilicon powder is added to 15wt% hydrogen peroxide aqueous solution, ultrasonically dispersed for 45 minutes, filtered, washed, and dried to obtain pretreated nanosilicon powder, wherein the ratio of nanosilicon powder to hydrogen peroxide aqueous solution is 1.5g:10mL; (3) Pretreated graphene is added to deionized water, ultrasonically dispersed for 45 minutes, and then pretreated nanosilicon powder is added thereto, stirred for reaction for 4 hours, filtered, washed, and dried to obtain graphene@nanosilicon powder material, wherein the mass ratio of pretreated graphene to pretreated nanosilicon powder is 0.2:1;

[0071] Step 3: Preparation of graphite @ graphene @ nano-silicon powder material: Sodium polyacrylate was added to deionized water and ultrasonically dispersed for 45 minutes, and then graphene @ nano-silicon powder material was added thereto, stirred and reacted for 4 hours, and freeze-dried, ground, and carbonized (under nitrogen gas protection, heating rate of 5°C / min, heating to 650°C, and keeping warm for 2 hours) to obtain graphite @ graphene @ nano-silicon powder material, wherein the mass ratio of sodium polyacrylate to graphene @ nano-silicon powder material was 2:1;

[0072] Step 4: Add graphite @ graphene @ nano silicon powder material, conductive carbon black and polytetrafluoroethylene in a mass ratio of 90:6:4 into a blender, stir and mix evenly to obtain a mixture; then add it to a roller press and roll it at 160°C to obtain a 200μm thick electrode film; attach the electrode film to both sides of a 12μm thick aluminum foil, and then roll it at 160°C to obtain a silicon-based negative electrode sheet.

[0073] Performance test: The silicon-based negative electrode sheets prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were assembled with the positive electrode ternary material (LiNi1 / 3Co1 / 3Mn1 / 3O2), electrolyte and diaphragm into a 5Ah soft-pack battery, wherein the diaphragm was celegard2400 and the electrolyte was a LiPF6 solution (the solvent was a mixed solution of EC and DEC with a volume ratio of 1:1, and the concentration of LiPF6 was 1.3 mol / L); and the assembled soft-pack battery was subjected to the following performance tests:

[0074] 1. Volume expansion rate: The volume expansion rate of the negative electrode sheet of each soft-pack battery corresponding to each example is tested at 25°C, a voltage range of 2.5-4.0V, and a rate of 1C after 100 cycles;

[0075] 2. Capacity retention: While testing the volume expansion rate, use a Neware battery tester to test the capacity retention of the soft-pack battery corresponding to each example after 100 cycles.

[0076] The test results of the above test contents are shown in Table 1 below:

[0077] Table 1

[0078] sample Volume expansion rate (%) Capacity retention rate (%) Example 1 9.6 93.4 Example 2 10.5 90.6 Example 3 10.0 92.1 Comparative Example 1 15.4 85.3 Comparative Example 2 13.5 87.2 Comparative Example 3 32.3 75.8 Comparative Example 4 18.8 83.4

[0079] Analysis of results: By comparing the data of the embodiment and the comparative example in Table 1 above, it can be seen that the present invention achieves the following: (1) introducing black phosphorus and graphene oxide, which synergistically strengthen the silicon-based negative electrode; (2) successively subjecting black phosphorus and graphene oxide to oxidation and reduction treatments, so that the black phosphorus / graphene composite material has a multi-scale, dense pore structure; (3) pre-treating the black phosphorus / graphene composite material and nano-silicon powder so that the coating between each layer structure becomes tight; the comprehensive preparation results in a silicon-based negative electrode sheet that can greatly adapt to the silicon volume expansion effect and improve the electrochemical performance.

[0080] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a silicon-based negative electrode sheet, characterized in that: The following steps are involved: Step 1: performing oxidation and reduction treatment on black phosphorus and graphene oxide to obtain a black phosphorus / graphene composite material with a porous structure; Step 2: Pre-treating the black phosphorus / graphene composite material and nano-silicon powder respectively, and then coating the nano-silicon powder with the black phosphorus / graphene composite material to obtain a black phosphorus / graphene@nano-silicon powder material; Step 3: adding the black phosphorus / graphene@nano-silicon powder material to the sodium polyacrylate solution, stirring the reaction, freeze-drying, grinding, and carbonizing to obtain the graphite@black phosphorus / graphene@nano-silicon powder material; Step 4: Mix the graphite@black phosphorus / graphene@nano-silicon powder material, conductive agent, and binder evenly, and roll-press to obtain an electrode film; attach the electrode film to both sides of the aluminum foil, and then roll-press to obtain a silicon-based negative electrode sheet.

2. The method for preparing a silicon-based negative electrode sheet according to claim 1, characterized in that: The preparation method of the black phosphorus / graphene composite material is: (1) adding black phosphorus and graphene oxide to N-methylpyrrolidone and ultrasonically dispersing for 1 to 6 hours to obtain a black phosphorus / graphene oxide dispersion; (2) heating the black phosphorus / graphene oxide dispersion to 50-70° C., adjusting its pH to 2-4, adding 20-40 wt % aqueous hydrogen peroxide solution thereto, stirring and reacting for 1-6 h to complete the oxidation treatment, and after naturally cooling to room temperature, filtering, washing, and drying to obtain a black phosphorus / graphene oxide oxidation product; (3) After heating a 50-70 wt% hydrazine hydrate aqueous solution to 80-100° C., adjusting its pH to 8-10, adding the black phosphorus / graphene oxide oxidation product thereto, stirring and reacting for 12-48 hours to complete the reduction treatment, and after naturally cooling to room temperature, filtering, washing, and drying to obtain a black phosphorus / graphene composite material.

3. The method for preparing a silicon-based negative electrode sheet according to claim 2, characterized in that: In the black phosphorus / graphene oxide dispersion, the concentration of black phosphorus is 1 to 5 mg / L, and the concentration of graphene oxide is 1 to 5 mg / L; The volume ratio of the black phosphorus / graphene oxide dispersion to the hydrogen peroxide aqueous solution is 10:(1-2); The ratio of the hydrazine hydrate aqueous solution to the black phosphorus / graphene oxide oxidation product is 10 mL: (1-2) g.

4. The method for preparing a silicon-based negative electrode sheet according to claim 1, wherein: The preparation method of the black phosphorus / graphene@nano silicon powder material is as follows: (1) Under inert gas protection, the black phosphorus / graphene composite material and the surfactant are added to isopropyl alcohol, ultrasonically dispersed for 30 to 60 minutes, filtered, washed, and dried to obtain a pretreated black phosphorus / graphene composite material; (2) adding the nano-silicon powder to a 10-20 wt% aqueous hydrogen peroxide solution, ultrasonically dispersing for 30-60 min, filtering, washing, and drying to obtain pretreated nano-silicon powder; (3) The pretreated black phosphorus / graphene composite material is added to deionized water and ultrasonically dispersed for 30 to 60 minutes, and then the pretreated nano-silicon powder is added thereto, stirred and reacted for 1 to 6 hours, and filtered, washed, and dried to obtain a black phosphorus / graphene@nano-silicon powder material.

5. The method for preparing a silicon-based negative electrode sheet according to claim 4, characterized in that: The surfactant is a cationic surfactant, and the amount added is 1-2% of the mass of the black phosphorus / graphene composite material; The ratio of the nano-silicon powder to the hydrogen peroxide solution is (1-2) g:10 mL; The mass ratio of the pretreated black phosphorus / graphene composite material to the pretreated nano-silicon powder is (0.1-0.3):

1.

6. The method for preparing a silicon-based negative electrode sheet according to claim 1, characterized in that: The preparation method of the graphite@black phosphorus / graphene@nano-silicon powder material comprises the following steps: adding sodium polyacrylate to deionized water, ultrasonically dispersing the mixture for 30 to 60 minutes, adding black phosphorus / graphene@nano-silicon powder material, stirring and reacting the mixture for 1 to 6 hours, and freeze-drying, grinding, and carbonizing the mixture to obtain the graphite@black phosphorus / graphene@nano-silicon powder material.

7. The method for preparing a silicon-based negative electrode sheet according to claim 6, characterized in that: The mass ratio of the sodium polyacrylate and black phosphorus / graphene@nano silicon powder materials is 2:1; The parameters of the carbonization treatment are: under inert gas protection, heating to 580-720° C. at a heating rate of 5° C. / min, and keeping the temperature for 1-3 hours.

8. The method for preparing a silicon-based negative electrode sheet according to claim 1, wherein: The mass ratio of the graphite@black phosphorus / graphene@nano silicon powder material, the conductive agent and the binder is (87-90):(5-7):(3-6).

9. The method for preparing a silicon-based negative electrode sheet according to claim 1, characterized in that: The rolling temperature is 150-180° C.; the thickness of the electrode film is 150-250 μm.

10. A silicon-based negative electrode sheet prepared by the method for preparing a silicon-based negative electrode sheet according to any one of claims 1 to 9.