Sodium-ion battery silicon dioxide molecular sieve composite negative electrode plate and preparation method thereof

Abstract

The invention discloses a sodium ion battery silicon dioxide molecular sieve composite negative electrode plate and a preparation method thereof. The preparation method comprises the following steps: preparing a coal gasification slag-based sodium ion battery soft carbon negative electrode material; manufacturing a soft carbon negative electrode material pole piece of the coal gasification slag-based sodium ion battery; preparing a silicon dioxide molecular sieve from a gasified slag silicon source; compounding a silicon dioxide molecular sieve on the surface of the soft carbon negative electrode material pole piece of the gasified slag-based sodium-ion battery; the surface of the prepared composite negative pole piece is a silicon dioxide molecular sieve; transmission of electrons on the surface of the negative electrode is improved, hindrance in the electron transmission process is reduced, interface resistance is reduced, and then the internal resistance of the battery is reduced; after the silicon dioxide molecular sieve is compounded on the surface of the soft carbon negative electrode material pole piece, the solvation structure of Na < + > ions in the sodium ion battery is adjusted, so that Na is uniformly deposited on the negative electrode surface, uniform inorganic-rich SEI is constructed, the generation probability of dendritic crystals is greatly reduced, and the safety of the whole battery is improved; and meanwhile, the overall charge-discharge performance, the rate capability and the cycle performance are greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of negative electrode materials and negative electrode sheets for sodium-ion batteries, and particularly relates to a sodium-ion battery silicon dioxide molecular sieve composite negative electrode sheet and a preparation method thereof. Background Art

[0002] Sodium-ion batteries have the characteristics of rich resources, high low-temperature performance, good safety, etc., and have irreplaceable advantages over lithium-ion batteries and lead-acid batteries in large-scale energy storage and low-temperature working conditions. Sodium-ion energy storage batteries are a revolution against the monopoly of lithium resources, with strategic significance higher than short-term economic benefits. Their expected cost will decrease with large-scale production, the cycle life will be further greatly improved, and the application space will be broader. They are the ultimate preferred devices for electrochemical energy storage.

[0003] However, the bottleneck of the sodium-ion battery industry chain lies in the negative electrode. The current types of negative electrodes and existing problems are as follows: 1: The resin-based one has the highest specific capacity, is the most suitable for controlling synthesis, but has extremely high costs and is difficult for large-scale production; 2: The biomass-based one has relatively excellent indicators, but the difficulty is that it is affected by the characteristics of biological sources, with poor batch stability and is difficult to scale up; 3: Anthracite has lower costs and the highest carbon yield, and the maturity of coal directly affects the quality. The first Coulomb efficiency is relatively low, and the capacity is relatively low; the problems existing in the currently prepared coal-based hard carbon negative electrode materials are: poor performance consistency, low capacity, low first efficiency, short cycle life, low rate performance, and prominent dendrite problems; the investment in high and low-temperature carbonization equipment is large; the large equipment investment, high-temperature process, and high energy consumption lead to high costs and low competitiveness; 4: The composition and structure of asphalt are highly controllable, with a high carbon yield and good conductivity. During production, it undergoes a liquid-solid two-phase process, but it is easy to generate glassy carbon and graphite.

[0004] The patent application with the publication number of CN 118738387A discloses an asphalt-coated space bamboo hard carbon sodium-ion battery negative electrode material and a preparation method thereof, in which asphalt is coated outside the space bamboo hard carbon material, and the mass ratio of asphalt to the space bamboo hard carbon material is 1:(3-9). Due to the difficulty in ensuring the consistency of the structure and performance of the prepared negative electrode material due to the sustainability and structural consistency of biomass raw materials, the application of the negative electrode material of this invention is difficult to achieve large-scale application. Summary of the Invention

[0005] In order to overcome the defects existing in the above prior art, the purpose of the present invention is to provide a sodium-ion battery silicon dioxide molecular sieve composite negative electrode sheet and a preparation method thereof. This preparation method uses silicon dioxide molecular sieve to prepare a composite electrode sheet, which desolvates sodium ions through its uniform and orderly pores, greatly improves the transmission of electrons on the surface of the negative electrode, reduces the hindrance in the electron transmission process, reduces the interfacial resistance, and further reduces the internal resistance of the battery; at the same time, it reduces the poor contact between the electrode and the electrolyte and improves the overall performance.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A preparation method of a sodium-ion battery silica molecular sieve composite negative electrode sheet, comprising the following steps:

[0008] Step 1: Select methanol and gasification slag generated during the gasification process of coal-to-oil production, and pre-grind the selected gasification slag;

[0009] Step 2: Physically float the ground gasification slag to obtain a first low-ash, high-carbon gasification slag and a second gasification slag;

[0010] Step 3: Perform pre-oxidation treatment on the first low-ash, high-carbon gasification slag;

[0011] Step 4: Coarsely grind the pre-oxidized first low-ash, high-carbon gasification slag;

[0012] Step 5: Finely grind the coarsely ground first low-ash, high-carbon gasification slag;

[0013] Step 6: Perform particle size proportioning on the finely ground first low-ash, high-carbon gasification slag;

[0014] Step 7: Acid wash the gasification slag after particle size proportioning with hydrochloric acid;

[0015] Step 8: Alkaline wash the gasification slag pickled with hydrochloric acid with NaOH;

[0016] Step 9: Treat the gasification slag alkaline washed with NaOH with hydrofluoric acid;

[0017] Step 10: Perform secondary pre-oxidation on the gasification slag treated with hydrofluoric acid to obtain a coal gasification slag-based sodium-ion battery soft carbon negative electrode material;

[0018] Step 11: Use the second gasification slag obtained by physical flotation in Step 2 as a precursor to prepare a silica molecular sieve;

[0019] Step 12: Prepare a silica molecular sieve composite slurry using the silica molecular sieve;

[0020] Step 13: Use the silica molecular sieve composite slurry and the coal gasification slag-based sodium-ion battery soft carbon negative electrode material to perform surface composite by a coating process to obtain a silica molecular sieve surface composite electrode sheet.

[0021] In Step 1, the pre-ground gasification slag is respectively coarse gasification slag and fine gasification slag. By mass ratio, the carbon content of the coarse gasification slag is 5%-25%, and the carbon content of the fine gasification slag is 15%-50%; the coarse gasification slag and the fine gasification slag are mixed in any proportion, and the particle size of the gasification slag minerals is concentrated between 10 and 350 microns.

[0022] In step 2, the specific steps of physical flotation include: vibrating screening, heavy medium flotation, and pressure filtration;

[0023] Vibrating screening screens out the gasified slag with a particle size between 125 - 500 microns. The gasified slag in this range has a relatively high carbon content and a specific surface area greater than 200 m 2 ·g -1 ;

[0024] The gasified slag with a particle size above 500 microns has an ash content as high as over 96.02% and is used as the raw material for the silica molecular sieve in step 11.

[0025] The gasified slag after vibrating screening is subjected to heavy medium flotation. A hydrocyclone is used to separate the gasified slag according to its density. The gasified slag with a low ash and high carbon content and a density of 1.10 - 1.30 g / cm 3 is separated out as the precursor for the anode material of the gasified slag-based sodium-ion battery;

[0026] The gasified slag with a high ash and low carbon content and a density greater than 1.30 g / cm 3 is separated out as the precursor for the silica molecular sieve;

[0027] The gasified slag after heavy medium flotation is subjected to pressure filtration using a plate-and-frame filter press to remove the main free water.

[0028] In summary, the two types of gasified slag obtained by physical flotation are:

[0029] In step 2, the first type of low-ash and high-carbon gasified slag is: with a particle size of about 120 - 500 microns, a specific surface area greater than 200 m 2 ·g -1 or so, a density of 1.10 - 1.30 g / cm 3 , a carbon content between 85% - 89%, and an ash content below 11% - 15%.

[0030] In step 2, the second type of gasified slag is: with a particle size above 500 microns, a density greater than 1.30 g / cm 3 , a carbon content below 2%, and an oxide content above 95%.

[0031] Step 3 is specifically as follows:

[0032] The first type of low-ash and high-carbon gasified slag is pre-oxidized using a pre-oxidation device. The pre-oxidation temperature is 100 - 500 °C, and the pre-oxidation time is 0.5 - 5 h;

[0033] The pre-oxidation device is limited to a rotary kiln pre-oxidation device, and the pre-oxidation device uses external heating or internal heating methods.

[0034] Step 4 is specifically as follows:

[0035] Crush the first low-ash, high-carbon gasification slag after pre-oxidation to a particle size of 50 - 100 microns;

[0036] The coarse grinding equipment uses a hammer crusher, but is not limited to a hammer crusher.

[0037] The specific operation of step 5 is as follows:

[0038] Fine grind the first low-ash, high-carbon gasification slag with a particle size of 50 - 100 microns to 1 - 20 microns;

[0039] Return the first low-ash, high-carbon gasification slag with a particle size above 20 microns for re-grinding;

[0040] The fine grinding equipment uses a Raymond mill crusher, but is not limited to a Raymond mill crusher.

[0041] The particle size in step 6 is proportioned as follows:

[0042] D10 is 1 micron; D50 is 5 microns; D90 is 15 microns; D100 is 20 microns.

[0043] The specific operation of step 7 is as follows:

[0044] Select a 10 - 30 wt% hydrochloric acid solution for treatment, with a treatment time of 4 - 8 h and a treatment temperature of 30 - 80 °C. Among them, the solid-liquid ratio of the gasification slag to the hydrochloric acid solution is 1:3 - 1:10. The purpose of this step is to wash away all alkaline oxides in the gasification slag, such as aluminum oxide, iron oxide, calcium oxide, magnesium oxide, etc.

[0045] The specific operation of step 8 is as follows:

[0046] Use a 3 - 5 wt% NaOH solution for alkali washing, with a treatment time of 6 - 10 h and a treatment temperature of 60 - 100 °C. Among them, the solid-liquid ratio of the gasification slag to the sodium hydroxide solution is 1:5 - 1:15. The purpose of this step is to wash away all acidic oxides in the gasification slag, such as silicon dioxide, etc.

[0047] The specific operation of step 9 is as follows:

[0048] Select a hydrofluoric acid solution with a mass concentration of 1 - 10 wt% for treatment, with a treatment time of 2 - 6 h and a treatment temperature of 60 - 80 °C. Among them, the solid-liquid mass ratio of the gasification slag to the hydrofluoric acid solution is 1:1 - 1:2.

[0049] The specific operation of step 10 is as follows:

[0050] Perform secondary pre-oxidation on the gasification slag after acid and alkali washing, with a pre-oxidation temperature of 100 - 500 °C;

[0051] The oxygen-containing functional groups introduced through pre-oxidation increase the active sites for sodium ion storage. The carbonyl functional groups generated during the pre-oxidation react with carboxyl groups through cross-linking and esterification reactions, increasing the disorder of the carbon structure and improving the sodium storage performance of the material.

[0052] The secondary pre-oxidation is not limited to the rotary kiln, and internal heating equipment or external heating equipment can be adopted.

[0053] The gasification slag-based soft carbon anode material for sodium-ion batteries is a granular powder with a rough surface, formed by the aggregation of small particles with a size of 1-20 microns, and is rich in pores inside. Under transmission electron microscopy, it can be observed that there are many short-range ordered graphite-like stripe domains inside the small particles, which is a typical crystal structure characteristic of soft carbon materials.

[0054] The preparation of the silica molecular sieve in Step 11 is specifically as follows:

[0055] Step (1): Mix a hydrochloric acid solution with a mass concentration of 2-3% with the second type of gasification slag described in Step 2 in a reaction kettle; stir at a temperature of 10°C to 80°C, and remove alkaline metal oxides through a water bath reaction to obtain a mixed slurry; among them, the solid-liquid mass ratio of the hydrochloric acid solution to the gasification slag is controlled between 1:1 and 1:15, and the stirring time lasts for 1-6 hours.

[0056] Step (2): Filter the mixed slurry to separate free water and gasification slag.

[0057] Step (3): Stir and mix the gasification slag described in Step (2) with a sodium hydroxide solution with a mass concentration of 2.5-3.5% in a reaction kettle and react, and then filter to obtain a filtrate; the solid-liquid mass ratio of the sodium hydroxide solution to the gasification slag is controlled between 1:2 and 1:15, the reaction temperature is maintained at 10°C - 100°C, and the hydrothermal reaction duration is 1-9 hours.

[0058] Step (4): Add the template agent to deionized water to prepare a template agent solution with a mass concentration of 0.05-0.2%; after uniformly stirring, gradually drop it into the filtrate described in Step (3) to obtain a synthesis solution of silicon source and template agent; among them, the mass ratio of the template agent solution to the filtrate is between 1:1 and 1:2; the template agent includes but is not limited to cetyltrimethylammonium bromide, dodecyl dimethyl benzyl ammonium chloride, and octadecyl dimethyl hydroxyethyl ammonium nitrate.

[0059] Step (5): Drop an acid solution into the synthesis solution obtained in Step (4) and transfer it to a reaction kettle to adjust the pH value of the solution to 10 to obtain a liquid; the acid solution includes but is not limited to dilute hydrochloric acid solution, dilute sulfuric acid solution, acetic acid solution, etc.

[0060] Step (6) ages the liquid at a temperature of 35°C - 45°C for 1 - 5 hours; during the aging process, as the chemical reaction proceeds, the structure of the molecular sieve gradually stabilizes and optimizes. The template agent molecules, through their specific spatial structure and charge distribution, guide the silicon-oxygen framework to form an ordered pore structure. At the same time, the physical and chemical changes during the aging process also help to remove some unstable components or structural defects, thereby improving the stability and performance of the molecular sieve.

[0061] Step (7): React the aged liquid at a hydrothermal reaction temperature of 100°C - 130°C for 3 - 72 hours to obtain a reactant; at this temperature, the hydrolysis and condensation reaction rates of the silicon source are moderate, which is conducive to the formation of a uniform silicon-oxygen framework and an ordered pore structure. At the same time, this temperature is also suitable for the interaction between the template agent and the silicon source, ensuring that the template agent can correctly guide the formation of the pores.

[0062] Step (8): Filter press or suction filter the reactant obtained in step (7) to obtain a powdery product; the silicon source and the template agent react fully to form MCM-41 with a mesoporous structure.

[0063] Step (9): Wash the powdery product with water until its pH reaches 7;

[0064] Step (10): Dry the neutral powdery product with a pH of 7, set the drying temperature between 50°C - 100°C, and the drying duration is 1 - 24 hours;

[0065] Step (11): Heat the dried product to 500°C - 600°C in an air atmosphere for 1 - 8 hours to remove the template agent, and then silica molecular sieve can be obtained.

[0066] The characteristic parameters of the silica molecular sieve are: specific surface area is 400 - 500 cm2 g-1, and average pore diameter is 4.5 - 5.0 nm.

[0067] The specific process of step 12 is as follows:

[0068] Step (1) Dissolve the binder in the solvent to obtain the first slurry, and the mass ratio of the binder to the solvent is 1:1 - 1:9;

[0069] Among them, the binder is polyvinylidene fluoride (PVDF), and the solvent is N-methylpyrrolidone;

[0070] Specifically, dissolve polyvinylidene fluoride in N-methylpyrrolidone to obtain the first slurry;

[0071] In the first slurry, the solvents include but are not limited to N-methylpyrrolidone, dimethylacetamide (DMAc), dimethylformamide (DMF), deionized water, etc.; the binders are also not limited to polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC).

[0072] In step (2), the silica molecular sieve is dispersed in the solvent NMP, and the mass ratio of the silica molecular sieve to the solvent NMP is 1:1 - 1:5 to prepare the second slurry; in the second slurry, the solvent is not limited to N-methylpyrrolidone, dimethylacetamide (DMAc), dimethylformamide (DMF), etc.

[0073] In step (3), the first slurry and the second slurry are mixed at a mass ratio of 1:1 - 1:2 and stirred for 1 - 24 hours to form a mixed slurry, obtaining the silica molecular sieve composite slurry.

[0074] In the said step (3), the viscosity of the silica molecular sieve composite slurry is 100 - 1000 CPS; controlling the viscosity can enable the negative electrode mixture with moderate viscosity to be evenly and stably coated on the current collector to form a uniform electrode layer, while reducing the internal resistance of the battery and increasing the electro-chemical reaction rate; the stirring temperature is controlled according to the process to be RT - 140 °C, and the electric heating method is adopted.

[0075] The said step 13 is specifically: coating the silica molecular sieve composite slurry and the coal gasification slag-based sodium ion battery soft carbon negative electrode material in step 10. First, coat the coal gasification slag-based sodium ion battery soft carbon negative electrode material on an aluminum foil or copper foil substrate, and then coat the silica molecular sieve composite slurry after drying to prepare a pole piece with silica molecular sieve compounded on the surface of the gasification slag-based soft carbon negative electrode material.

[0076] The coating process of the composite pole piece is: unrolling, preheating, coating, baking, and reeling; the specific steps are as follows:

[0077] Step (1): Place the copper foil or aluminum foil substrate on the unrolling device, and automatically correct the deviation and enter the unrolling tension system.

[0078] Step (2): After adjusting the unrolling tension, enter the preheating oven for preheating; the preheating temperature is 60 - 80 °C.

[0079] Step (3): When the substrate reaches the coating head, the composite pole piece is coated according to the set program of the coating system.

[0080] Step (4): The wet pole piece after coating enters the oven and is dried by hot air.

[0081] Step (5): After drying, the tension of the composite pole piece is adjusted by the tension system, and at the same time, the reeling speed is controlled to make it synchronous with the coating speed.

[0082] In step (6), the composite pole piece is automatically rectified by a rectification system to keep it in a set position, and is wound by a winding device.

[0083] Among them, the thickness of the copper foil or aluminum foil substrate in step (1): 7 - 20 μm;

[0084] In the composite pole piece of step (6), the wet thickness of the silica molecular sieve coating: (2 - 13) μm (single-sided wet thickness); double-sided coating is adopted;

[0085] The dry thickness of the silica molecular sieve coating: (1 - 4) μm (single-sided dry thickness); double-sided coating is adopted;

[0086] The dry coating thickness of the gasification slag-based soft carbon anode material is 50 - 300 μm;

[0087] The thickness ratio of the gasification slag-based soft carbon anode material to the silica molecular sieve coating is 20:1 - 5:1.

[0088] The coating method adopted in step (4): slot die extrusion coating;

[0089] The preheating and baking temperature in step (4) is: 50 - 140 degrees.

[0090] A sodium-ion battery silica molecular sieve composite negative pole piece, the surface layer is silica molecular sieve, the middle layer is a coal-based gasification slag soft carbon anode material, and the bottom layer is an aluminum conductive substrate; the surface of the coal-based gasification slag soft carbon anode material is a uniform solid electrolyte interface rich in inorganic substances.

[0091] The silica molecular sieve is a long-range ordered mesoporous material, having a uniform pore size, a high specific surface area, a large adsorption capacity, and a uniform mesoporous structure, with a specific surface area of 400 - 500 m 2 / g, a pore volume of 0.4 - 0.6 cm3 / g, the particle size of the molecular sieve is 150 - 200 nm, and its pore channels are hexagonally ordered, with a pore diameter of 4 - 5 nm.

[0092] The sodium-ion battery silica molecular sieve composite negative pole piece is applied to the negative pole of a sodium-ion battery cell. The negative pole of the sodium-ion battery cell includes a cylindrical sodium-ion battery cell negative pole, a square shell sodium-ion battery cell negative pole, or a soft-pack sodium-ion battery cell negative pole; after a series of battery cells are manufactured, they are assembled into modules and PACKs, and combined into a battery pack and an energy management system for large-scale energy storage, industrial and commercial energy storage, distributed energy storage, or a power battery system.

[0093] Compared with the prior art, the beneficial effects of the present invention are:

[0094] The resources of the present invention are abundant, with an annual output of over hundreds of millions of tons, capable of building an industrial base for sodium-ion soft carbon anode materials based on gasification slag with a scale of millions of tons and its composite electrodes with silica molecular sieve from gasification slag silicon source, significantly improving the consistency of the performance of sodium-ion battery composite electrodes;

[0095] Gasification slag can be processed by low-cost physical flotation and other means, which can significantly increase the silica content of the silica source in gasification slag, and the silica content can be increased to 50%-80%; the carbon content of the gasification slag-based soft carbon anode material precursor can also reach more than 85%;

[0096] Through the selection of gasification slag, physical flotation, and the preparation of silica molecular sieve; the characteristic parameters of the prepared silica molecular sieve are: the molecular sieve is a long-range ordered mesoporous material with uniform pore size, high specific surface area, large adsorption capacity, and uniform mesoporous structure. Its pore channels are arranged in a hexagonal order, with a specific surface area of 400-500 cm2 / g, the particle size of the molecular sieve is 150-200 nm, and the average pore diameter is 4.5-5.0 nm;

[0097] Using the composite electrode of gasification slag silicon source silica molecular sieve can significantly improve the wettability of the electrolyte, thereby promoting the smooth migration of sodium ions and improving the electrochemical properties;

[0098] Significantly improve the sodium-ion conductivity and liquid absorption rate of the composite electrode, so that when the composite electrode is used in sodium-ion batteries, it shows high battery capacity and cycle stability; the capacity of the half-cell composed of the composite electrode and the gasification slag-based sodium-ion battery soft carbon anode material increases from the original 500 mAh / g to more than 700 mAh / g, and the reversible capacity increases from the original 260 to more than 330 mAh / g;

[0099] Using the composite electrode of gasification slag silicon source silica molecular sieve can significantly increase the effective capacity of the gasification slag-based soft carbon anode material of sodium-ion batteries; the slope capacity of the discharge curve increases from the original 200 mAh / g to more than 260 mAh / g;

[0100] Using the gasification slag silicon source silica molecular sieve to perform surface composite on the gasification slag-based soft carbon anode electrode can significantly improve the high-rate charge and discharge performance: under the 2C charge and discharge rate, the performance of the gasification slag-based anode material is more than 10 times that of the anode materials of organic precursors such as coconut shell and pitch;

[0101] Using the composite electrode of gasification slag silicon source silica molecular sieve, due to the very stable mesoporous structure and silicon-oxygen bond of the silica molecular sieve prepared from gasification slag silicon source, the cycle life is significantly improved: the cycle life of the gasification slag-based soft carbon anode material is expected to reach more than 10,000 times from the original more than 6,000 times;

[0102] The silica molecular sieve prepared from the gasification slag silicon source has a mesoporous structure (3 - 5 nm) and a three-dimensional through-connected three-dimensional structure, which is conducive to the rapid passage of sodium ions during charge and discharge, and is suitable for high-rate charge and discharge; the charge and discharge speed is more than 10 times that of ordinary hard carbon and soft carbon.

[0103] The pore diameter of the silica molecular sieve in the composite electrode is 3 - 5 nm. Due to the scale effect of the nanochannels, the transport of Na+ is more strictly restricted and regulated, avoiding problems of uneven flow rate and ion concentration gradient, resulting in a more uniform Na+ flow rate, and the current density is uniform during battery operation, especially at high rates, without inducing the growth of lithium dendrites, which would affect the battery performance or even cause safety accidents.

[0104] The surface of the mesoporous channel wall has negative charges, which further improves the + transport speed and efficiency of Na in the channels, greatly increasing the ionic conductivity.

[0105] In the nanochannels, due to the increase in ion concentration and the acceleration of transport speed, more contact ion pairs and ion aggregates are formed. These structures gradually deposit on the channel walls and successfully build a uniform SEI rich in inorganic substances; this SEI layer not only has excellent stability and compactness but also can effectively prevent the co-insertion of solvent molecules, thus avoiding the damage to the electrode material caused by the co-insertion of solvent molecules.

[0106] The silica molecular sieve also weakens the interaction between the electrolyte solvent and sodium ions, reduces the dissolution energy of sodium ions in the solvent, and ultimately leads to the uniform deposition of sodium metal in the channels, avoiding the generation of sodium dendrites, thereby improving the safety of sodium batteries. Description of the Drawings

[0107] Figure 1 It is a scanning electron microscope image of the coal-based gasification slag soft carbon negative electrode material and the molecular sieve composite electrode.

[0108] Figure 2 It is a scanning electron microscope image of the silica molecular sieve; among them, Figure 2 (a) is the scanning electron microscope image of the silica molecular sieve, Figure 2 (b) is Figure 2 (a) partial schematic diagram.

[0109] Figure 3 It is a high-resolution image of the molecular sieve.

[0110] Figure 4 It is the surface morphology of the uncomposite electrode.

[0111] Figure 5 It is the surface morphology image after composite.

[0112] Figure 6 is the pre - composite solvation structure.

[0113] Figure 7 is the post - composite solvation structure.

[0114] Figure 8 is the SEI film generated on the surface of the negative electrode plate before composite.

[0115] Figure 9 is the SEI film generated on the surface of the negative electrode plate after composite.

[0116] Figure 10 is the charge - discharge curve graph.

[0117] Figure 11 is the rate performance graph at 4C. Specific embodiments

[0118] The present invention will be further described in detail below with reference to the accompanying drawings.

[0119] Example 1:

[0120] Step 1: Select the flotation gasification slag

[0121] Step 1) Select the gasification slag: By mass ratio, the carbon content of the gasification slag is 25%; the particle size is between 10 and 1200 microns; the density is 1.3 g / cm 3 ;

[0122] Step 2) Use a vibrating screen to separate out the gasification slag with high - content silica above 500 microns;

[0123] Step 3) Conduct heavy - medium separation using a hydrocyclone: Hydrocyclone out the gasification slag with a density of 1.3 g / cm 3 , a silica content of 60%, and a carbon content of 1.5%; and conduct pressure filtration to filter out free water;

[0124] Step 2: Preparation of silica molecular sieve

[0125] Step 1) Prepare a hydrochloric acid solution with a mass concentration of 2.5%, and stir and mix it with the gasification slag in a reaction kettle; control the solid - liquid ratio at 1:5, the temperature at 25°C, and the stirring time for 1 hour, and conduct a water - bath reaction to remove alkaline metal oxides; conduct pressure filtration on the mixed reaction slurry to separate free water and the gasification slag;

[0126] Step 2) Prepare a sodium hydroxide solution with a mass concentration of 2%; stir, mix, and react the gasification slag with the sodium hydroxide liquid in a reaction kettle; control the solid - liquid ratio at 1:3, the reaction temperature at 25°C, and the hydrothermal reaction duration at 1 hour;

[0127] Step 3) Add the template agent into deionized water to prepare a template agent solution with a mass concentration of 0.05%. Select 12 ml of the template agent solution with a mass concentration of 0.05%, stir it evenly and gradually drop it into the 15 ml of the filtrate obtained in step 2). The template agent is cetyltrimethylammonium bromide;

[0128] Step 4) Drop dilute hydrochloric acid into the reaction kettle to adjust the pH value of the solution to 10; and age the liquid at a temperature of 35 °C for 1 hour;

[0129] Step 5) React the liquid at a hydrothermal reaction temperature of 100 °C for 3 hours; filter press the liquid to obtain a powdery product; wash the powdery product with water until it reaches neutral;

[0130] Step 6) Dry the powdery product at 50 °C for 1 hour;

[0131] Step 7) Heat the dried powdery product to 500 °C in an air atmosphere for 1 hour to remove the template agent, and then silica molecular sieve can be obtained;

[0132] The characteristic parameters of the prepared silica molecular sieve are: specific surface area is 410 cm2 g-1, and average pore diameter is 4.5 nm.

[0133] Step 3: Preparation of silica molecular sieve slurry

[0134] Step 1) Dissolve 1 g of polyvinylidene fluoride (PVDF, binder) in 9 g of N-methylpyrrolidone (NMP, solvent);

[0135] Step 2) Disperse the gasification slag silicon source silica molecular sieve in the solvent NMP, and the mass ratio of the two is 1:3;

[0136] Step 3) Mix the slurries obtained in step 1) and step 2) according to a mass ratio of 1:1 and stir for 1 hour, with the stirring time being 1 hour; Viscosity control: 500 CPS; Stirring temperature: room temperature;

[0137] Step 4, Coating, Baking

[0138] Step 1) The composite electrode substrate is aluminum foil. On the unwinding device, it is automatically corrected and enters the unwinding tension system;

[0139] Step 2) After adjusting the unwinding tension, enter the preheating oven for preheating. The preheating temperature is 80 °C and the preheating time is 1 hour;

[0140] Step 3) When the substrate reaches the coating head, the composite electrode is coated according to the set program of the coating system; The coating speed is 1 m / min;

[0141] Step 4) The wet electrode sheet after coating enters the oven and is dried by hot air. The hot air temperature is 90°C, and the drying time is 1 hour.

[0142] Step 5) The tension of the dried composite electrode sheet is adjusted by the tension system, and at the same time, the winding speed is controlled to make the winding speed synchronous with the coating speed.

[0143] Step 6) The composite electrode sheet is automatically corrected by the deviation correction system to keep the composite electrode sheet in the set position, and is wound by the winding device.

[0144] The thickness of the aluminum foil substrate: 15 μm;

[0145] The coating thickness of the gasification slag-based soft carbon anode material is 50 μm (single-sided thickness); double-sided coating;

[0146] The wet thickness of the silica molecular sieve coating: 12 μm (single-sided wet thickness); double-sided coating;

[0147] The dry thickness of the silica molecular sieve coating is 4 μm (single-sided dry thickness); double-sided coating.

[0148] Finally, a silica molecular sieve composite negative electrode sheet for a sodium-ion battery is obtained.

[0149] Example 2:

[0150] Step 1: Select the flotation gasification slag

[0151] Step 1) Select the gasification slag: By mass ratio, the selected gasification slag has a carbon content of 20%; the particle size is between 100 and 1200 microns; the density is 1.2 g / cm 3 ;

[0152] Step 2) The gasification slag with a high silica content above 500 microns is separated by a vibrating screen;

[0153] Step 3) Use a hydrocyclone for heavy medium separation: The gasification slag with a density of 1.2 g / cm 3 , a silica content of 60%, and a carbon content of 1.6% is cycloned out; and it is pressure-filtered to filter out free water;

[0154] Step 2: Preparation of silica molecular sieve

[0155] Step 1) Prepare a solution with a hydrochloric acid mass concentration of 2.5%, and stir and mix it with the gasification slag in a reaction kettle; the solid-liquid ratio is controlled at 1:6, the temperature is controlled at 20°C, the stirring time lasts for 1.5 hours, and the alkaline metal oxides are removed by a water bath reaction; the mixed reaction slurry is pressure-filtered to separate free water and gasification slag;

[0156] Step 2) Prepare a sodium hydroxide solution with a mass concentration of 2.5%; stir and mix the gasification slag and the sodium hydroxide liquid in a reaction kettle for reaction; control the solid-liquid ratio at 1:4, the reaction temperature at 25 °C, and the hydrothermal reaction duration at 2 hours;

[0157] Step 3) Add the template agent to deionized water to prepare a template agent solution with a mass concentration of 0.07%. Select 12 ml of the template agent solution with a mass concentration of 0.07% and gradually drop it into 15 ml of the filtrate obtained in Step 2) while stirring evenly. The template agent is dodecyl dimethyl benzyl ammonium chloride;

[0158] Step 4) Drop a dilute sulfuric acid solution into the reaction kettle to adjust the pH value of the solution to 10; and age the liquid at a temperature of 35 °C for 2 hours;

[0159] Step 5) React the liquid at a hydrothermal reaction temperature of 110 °C for 4 hours; filter press the liquid to obtain a powdery product; wash the powdery product with water until it reaches neutral;

[0160] Step 6) Dry the powdery product at 60 °C for 2 hours;

[0161] Step 7) Heat the dried powdery product to 510 °C in an air atmosphere for 2 hours to remove the template agent, and then silica molecular sieve can be obtained;

[0162] The characteristic parameters of the prepared silica molecular sieve are: specific surface area is 430 cm2 g-1, and average pore diameter is 4.56 nm.

[0163] Step 3: Preparation of Coating Slurry

[0164] Step 1) Dissolve 0.5 g of polyvinylidene fluoride (PVDF, binder) in 9 g of N-methylpyrrolidone (NMP, solvent);

[0165] Step 2) Disperse the gasification slag silicon source silica molecular sieve in the solvent NMP, and the mass ratio of the two is 1:4;

[0166] Step 3) Mix the slurries obtained in Step 1) and Step 2) according to a mass ratio of 1:2 and stir for 2 hours; control the viscosity: 200 CPS; the stirring temperature is room temperature;

[0167] Step 4, Coating, Baking

[0168] Step 1) The electrode substrate is aluminum foil. On the unwinding device, it is automatically corrected and enters the unwinding tension system;

[0169] Step 2) After adjusting the unwinding tension, enter the preheating oven for preheating. The preheating temperature is 80 degrees, and the preheating time is 1 hour;

[0170] Step 3) The substrate reaches the coating head, and the composite electrode is coated according to the set program of the coating system; the coating speed is 1 m / min;

[0171] Step 4) The wet electrode after coating enters the oven and is dried by hot air. The hot air temperature is 100 °C and the drying time is 1 hour;

[0172] Step 5) The tension of the dried composite electrode is adjusted by the tension system, and at the same time, the winding speed is controlled to make the winding speed synchronous with the coating speed;

[0173] Step 6) The composite electrode is automatically corrected by the deviation correction system to keep the composite electrode in the set position and is wound by the winding device.

[0174] The thickness of the aluminum foil substrate: 15 μm;

[0175] The coating thickness of the gasification slag-based soft carbon anode material is 100 μm (single-sided thickness); double-sided coating;

[0176] The wet thickness of the silica molecular sieve coating: 11 μm (single-sided wet thickness); double-sided coating;

[0177] The dry thickness of the silica molecular sieve coating: 3 μm (single-sided dry thickness); double-sided coating;

[0178] Finally, a silica molecular sieve composite negative electrode for a sodium-ion battery is obtained.

[0179] Example 3:

[0180] Step 1: Select the flotation gasification slag

[0181] Step 1) By mass ratio, the selected gasification slag has a carbon content of 50%; the particle size is between 100 and 1200 microns; the density is 1.1 g / cm 3 ;

[0182] Step 2) The gasification slag with a high content of silica above 500 microns is separated by a vibrating screen;

[0183] Step 3) Heavy medium separation is carried out using a hydrocyclone: the gasification slag with a density of 1.1 g / cm 3 , a silica content of 56%, and a carbon content of 1.8% is cycloned out; and pressure filtration is carried out to filter out free water;

[0184] Step 2: Preparation of silica molecular sieve

[0185] Step 1) Prepare a solution with a hydrochloric acid mass concentration of 3% and stir and mix it with the gasification slag in a reaction kettle; the solid-liquid ratio is controlled at 1:7, the temperature is controlled at 25 °C, the stirring time lasts for 2 hours, and the alkaline metal oxides are removed by a water bath reaction; the mixed reaction slurry is pressure-filtered to separate free water and gasification slag;

[0186] Step 2) Prepare a sodium hydroxide solution with a mass concentration of 3%; stir and mix the gasification slag and the sodium hydroxide liquid in a reaction kettle for reaction; control the solid-liquid ratio at 1:6, the reaction temperature at 25°C, and the hydrothermal reaction duration at 2 hours;

[0187] Step 3) Add the template agent to deionized water to prepare a template agent solution with a mass concentration of 0.1%; select 12 ml of the template agent solution with a mass concentration of 0.1%, stir evenly and gradually drop it into 15 ml of the filtrate obtained in Step 2). The template agent is selected as octadecyl dimethyl hydroxyethyl ammonium nitrate;

[0188] Step 4) Drop acetic acid solution into the reaction kettle to adjust the pH value of the solution to 10; and age the liquid at a temperature of 35°C for 3 hours;

[0189] Step 5) React the liquid at a hydrothermal reaction temperature of 110°C for 4 hours; filter press the liquid to obtain a powdery product; wash the powdery product with water until it reaches neutral;

[0190] Step 6) Dry the powdery product at 70°C for 2 hours;

[0191] Step 7) Heat the dried powdery product to 560°C in an air atmosphere for 2 hours to remove the template agent, and then silica molecular sieve can be obtained;

[0192] The characteristic parameters of the prepared silica molecular sieve are: specific surface area is 420 cm2 g-1, and average pore diameter is 4.7 nm.

[0193] Step 3: Preparation of Coating Slurry

[0194] Step 1) Dissolve 2 g of polyvinylidene fluoride (PVDF, binder) in 9 g of N-methylpyrrolidone (NMP, solvent);

[0195] Step 2) Disperse the gasification slag silicon source silica molecular sieve in the solvent NMP, and the mass ratio of the two is 1:5;

[0196] Step 3) Mix and stir the slurries obtained in Step 1) and Step 2) according to a mass ratio of 1.5:1 for 3 hours; control the viscosity: 300 CPS; the stirring temperature is room temperature;

[0197] Step 4, Coating, Baking

[0198] Step 1) The composite electrode substrate is aluminum foil. On the unwinding device, it is automatically corrected and enters the unwinding tension system;

[0199] Step 2) After adjusting the unwinding tension, enter the preheating oven for preheating. The preheating temperature is 70°C, and the preheating time is 1 hour.

[0200] Step 3) When the base material reaches the coating head, the composite electrode is coated according to the set program of the coating system; the coating speed is 1 m / min.

[0201] Step 4) The wet electrode after coating enters the oven and is dried by hot air. The hot air temperature is 100°C, and the drying time is 1 hour.

[0202] Step 5) After drying, the tension of the composite electrode is adjusted by the tension system, and at the same time, the winding speed is controlled to make the winding speed synchronous with the coating speed.

[0203] Step 6) The composite electrode is automatically corrected by the deviation correction system to keep the composite electrode in the set position and is wound by the winding device.

[0204] Thickness of aluminum foil base material: 15 μm

[0205] The coating thickness of the gasification slag-based soft carbon anode material is 200 μm (single-sided thickness); double-sided coating.

[0206] Wet thickness of the silica molecular sieve coating: 10 μm (single-sided wet thickness); double-sided coating.

[0207] Dry thickness of the silica molecular sieve coating: 2 μm (single-sided dry thickness); double-sided coating.

[0208] Finally, a silica molecular sieve composite negative electrode for a sodium-ion battery is obtained.

[0209] The composite electrode obtained in the example has the following characteristics:

[0210] 1. The surface of the gasification slag soft carbon anode material electrode is uneven and presents a blocky structure, while the surface of the silica molecular sieve composite negative electrode is smoother and flatter.

[0211] 2. The smooth and flat surface helps the transmission of electrons on the negative electrode surface, reduces the hindrance during the electron transmission process, lowers the interfacial resistance, and thus reduces the internal resistance of the battery.

[0212] 3. The smooth and flat electrode surface greatly reduces the poor contact between the electrode and the electrolyte, improving the overall performance.

[0213] 4. After the silica molecular sieve is compounded on the surface of the soft carbon anode material, the solvation structure of Na+ ions in the sodium-ion battery is adjusted.

[0214] 5. Adjusting the solvation structure presents a state with more contact ion pairs.

[0215] 6. Adjusting the solvation structure presents a state with more ion aggregates.

[0216] 7: Adjusting the solvation structure can construct a uniform inorganic-rich SEI in the anode of a sodium-ion battery;

[0217] 8: The adjusted solvation structure weakens the interaction between the solvent and Li+, resulting in a lower desolvation energy for Li+, enabling uniform deposition of Na on the negative electrode surface;

[0218] 9: Greatly reduces the probability of dendrite formation, significantly reduces the probability of the diaphragm being punctured by dendrites, avoids short-circuit fire combustion and explosion accidents, and greatly improves the overall safety of the battery;

[0219] 10: Greatly improves the charge-discharge performance. The charge-discharge curves of the soft carbon negative electrode material based on gasification slag and the surface composite negative electrode material and electrode sheet of carbon dioxide molecular sieve for the sodium-ion battery show that the first charge is 700 mAh / g and the reversible capacity is 330 mAh / g; at the same time, the shape of the charge-discharge curve is changed, and the slope capacity is above 260 mAh / g;

[0220] 11: Due to the surface composite of silica and the coal-based gasification slag-based negative electrode material, the shape of the charge-discharge curve is changed, and the slope capacity is above 260 mAh / g, greatly improving the rate performance of the composite negative electrode sheet. The performance of the composite negative electrode sheet at a 4C current density is more than 10 times the charge-discharge capacity of coconut shell, pitch, etc.

[0221] Figure 1 This is the scanning electron microscope image of the molecular sieve composite electrode sheet of Example 1 of the present invention. The surface layer is silica molecular sieve, the middle layer is the coal-based gasification slag soft carbon negative electrode material, and the bottom layer is the aluminum conductive substrate;

[0222] Figure 2 (a), Figure 2 (b), Figure 3 are the scanning electron microscope image and high-resolution image of the silica molecular sieve of Example 1 of the present invention; the molecular sieve is a long-range ordered mesoporous material with a uniform pore size, high specific surface area, large adsorption capacity, and uniform mesoporous structure. The specific surface area reaches 400 - 500 m 2 / g, large pore volume, particle size between 150 - 200 nm, as Figure 2 shown in the scanning electron microscope; its pore channels are hexagonally ordered, and the pore diameter is between 4 - 5 nm, as Figure 3 shown in the high-resolution photo.

[0223] Figure 4 , Figure 5 are the scanning electron microscope images of the surface morphology of the coal-based gasification slag soft carbon negative electrode sheet before and after composite of Example 1 of the present invention; after composite with silica molecular sieve, the roughness of the electrode sheet surface is greatly reduced, improving the smoothness and flatness; Figure 4 is the surface morphology of the uncomposite electrode sheet, Figure 4It shows that the surface of the uncomposite negative electrode plate is severely uneven; Figure 5 is the surface morphology diagram after composite; Figure 5 It shows that the surface of the composite electrode plate is relatively smooth; the improvement of smoothness and flatness greatly improves the transmission of electrons on the negative electrode surface, reduces the hindrance during the electron transmission process, reduces the interface resistance, and thus reduces the internal resistance of the battery; at the same time, it reduces the poor contact between the electrode and the electrolyte and improves the overall performance.

[0224] Figure 6 、 Figure 7 is the change diagram of the solvation structure of Example 1 of the present invention; after the silica molecular sieve is composited on the surface of the soft carbon negative electrode material, the solvation structure of Na + ions in the sodium ion battery is adjusted; Figure 6 is the solvation structure before composite. The solvation structure is that Na+ is dissolved by the solvent to form a solvation sheath, and the anion is separated outside the solvation sheath.

[0225] Figure 7 is the solvation structure after composite of Example 1 of the present invention. Its structure presents an aggregated state, containing more contact ion pairs and ion aggregates. These structures will successfully construct a uniform solid electrolyte interface rich in inorganic substances on the sodium negative electrode.

[0226] Figure 8 、 Figure 9 is the morphology of the SEI film before and after adjusting the solvation structure of Example 1 of the present invention; a uniform inorganic-rich SEI is constructed on the surface of the composite electrode plate of the coal-based gasification slag soft carbon negative electrode material. Figure 8 It shows the SEI film before composite. The SEI film is uneven, and the SEI at local positions is very prominent; Figure 9 is the SEI film after composite. The film is relatively uniform; the adjusted solvation structure weakens the interaction between the solvent and Na + , resulting in a lower desolvation energy of Na + , making the deposition of Na on the negative electrode surface uniform; the composite electrode plate greatly reduces the probability of dendrite generation, greatly reduces the probability of the diaphragm being punctured by dendrites, avoids short-circuit fire, combustion and explosion accidents, and greatly improves the safety of the overall battery.

[0227] Figure 10 is the charge-discharge curve of the composite electrode plate of Example 1 of the present invention; the coal-based gasification slag soft carbon negative electrode composite electrode plate greatly improves the charge-discharge performance: the first charge of the gasification slag-based sodium ion battery soft carbon negative electrode material and the surface composite negative electrode material and electrode plate is 700 mAh / g, and the reversible capacity is above 330 mAh / g; as Figure 10 shown.

[0228] Figure 11Charge and discharge performance comparison chart of the coal-based gasification slag soft carbon negative composite electrode and coconut shell-based and pitch-based electrodes under high rate conditions for Example 1 of the present invention; the slope capacity of the composite electrode reaches more than 260 mAh / g, which will greatly improve the high rate performance of the battery; the charge and discharge capacity of the composite negative electrode at a current density of 4C is more than 10 times that of hard carbon negative electrode materials such as coconut shell-based and pitch-based; as Figure 11 shown.

Claims

1. A method for preparing a sodium ion battery silicon dioxide molecular sieve composite negative electrode plate, characterized in that: The following steps are involved: Step 1: Select gasification slag produced in the gasification process of methanol and coal-to-liquid manufacturing, and pre-grind the selected gasification slag; Step 2: Physically float the ground gasified slag to obtain low-ash, high-carbon gasified slag; Step 3: pre-oxidizing the first low-ash, high-carbon gasified slag; Step 4: coarsely grinding the first low-ash, high-carbon gasified slag after pre-oxidation; Step 5: finely grinding the first low-ash, high-carbon gasified slag after coarse grinding; Step 6: The first low-ash, high-carbon gasified slag after fine grinding is subjected to particle size ratio matching to increase the compaction density of the pole piece and improve the volume energy density of the battery; Step 7: washing the gasified slag with hydrochloric acid after the particle size ratio is performed; Step 8: washing the gasified slag after the hydrochloric acid pickling with NaOH; Step 9: treating the gasified slag washed with NaOH with hydrofluoric acid; Step 10: performing secondary pre-oxidation on the gasified slag after the hydrofluoric acid treatment to obtain a coal gasification slag-based sodium ion battery soft carbon negative electrode material; Step 11: using the low-ash, high-carbon gasified slag obtained by physical flotation in step 2 as a precursor to prepare a silicon dioxide molecular sieve; Step 12: using the silica molecular sieve to prepare a silica molecular sieve composite slurry; Step 13: Use the silica molecular sieve composite slurry and the coal gasification slag-based sodium ion battery soft carbon negative electrode material to perform surface composite using a coating process to obtain a silica molecular sieve surface composite electrode sheet.

2. The method for preparing a sodium ion battery silicon dioxide molecular sieve composite negative electrode sheet according to claim 1, characterized in that: In the step 1, the pre-grinded gasified slag is respectively coarse gasified slag and fine gasified slag, and the carbon content of the coarse gasified slag is 5%-25% by mass, and the carbon content of the fine gasified slag is 15-50% by mass; the coarse gasified slag and the fine gasified slag are mixed in any proportion, and the mineral particle size of the gasified slag is concentrated between 10 and 350 microns; In step 2, the first low-ash, high-carbon gasified slag has a particle size of about 120-500 microns and a specific surface area of ​​more than 200m 2 ·g -1 About, density is 1.10-1.30g / cm 3 , the carbon content is between 85% and 89%, and the ash content is below 11% to 15%; In step 2, the second gasified slag has a particle size of more than 500 microns and a density of more than 1.30 g / cm 3 , the carbon content is less than 2% and the oxide content is more than 95%.

3. The method for preparing a sodium ion battery silicon dioxide molecular sieve composite negative electrode sheet according to claim 2, characterized in that: The step 3 is specifically as follows: The first low-ash, high-carbon gasified slag is pre-oxidized by using pre-oxidation equipment, the pre-oxidation temperature is 100-500°C, and the pre-oxidation time is 0.5-5h; The step 4 is specifically as follows: Crushing the first low-ash, high-carbon gasified slag after pre-oxidation to a particle size of 50-100 microns; The step 5 is specifically as follows: Grind the first low-ash, high-carbon gasified slag with a particle size of 50-100 microns into 1-20 microns; The first type of low-ash, high-carbon gasified slag above 20 microns is returned for further grinding; The particle size of step 6 is proportioned in the following manner: D10 is 1 micron; D50 is 5 microns; D90 is 15 microns; D100 is 20 microns.

4. The method for preparing a sodium ion battery silicon dioxide molecular sieve composite negative electrode sheet according to claim 3, characterized in that: The step 7 is specifically as follows: Select 10-30wt% hydrochloric acid solution for treatment, the treatment time is 4-8h, the treatment temperature is 30-80°C, wherein the solid-liquid ratio of gasified slag to hydrochloric acid solution is 1:3-1:10; The step 8 is specifically as follows: Use NaOH with a concentration of 3-5wt% for alkaline washing, the treatment time is 6-10h, the treatment temperature is 60-100°C, wherein the solid-liquid ratio of gasified slag to sodium hydroxide solution is 1:5-1:15; The step 9 is specifically as follows: A hydrofluoric acid solution with a mass concentration of 1-10wt% is selected for treatment, the treatment time is 2-6h, the treatment temperature is 60-80°C, wherein the solid-liquid mass ratio of the gasified slag to the hydrofluoric acid solution is 1:1-1:2; The step 10 is specifically as follows: The gasified slag after acid and alkali washing is subjected to secondary pre-oxidation at a temperature of 100-500°C.

5. The method for preparing a sodium ion battery silicon dioxide molecular sieve composite negative electrode sheet according to claim 4, characterized in that: The step 11 specifically comprises: preparing a gasified slag silicon source silica molecular sieve; Step (1): mixing a hydrochloric acid solution having a mass concentration of 2-3% with the second gasified slag in step 2 in a reactor; stirring at a temperature of 10° C. to 80° C., removing alkaline metal oxides by water bath reaction, and obtaining a mixed slurry; wherein the mass ratio of the hydrochloric acid solution to the gasified slag solid-liquid is controlled between 1:1 and 1:15, and the stirring time is continued for 1 to 6 hours; Step (2): filtering the mixed slurry to separate free water and gasified slag; Step (3): stirring, mixing and reacting the gasified slag in step (2) with a sodium hydroxide solution having a mass concentration of 2.5-3.5% in a reactor, and filtering to obtain a filtrate; the solid-liquid mass ratio of the sodium hydroxide solution to the gasified slag is controlled between 1:2 and 1:15, the reaction temperature is maintained at 10° C.-100° C., and the hydrothermal reaction time is 1-9 hours; Step (4): adding a template to deionized water to prepare a template solution with a mass concentration of 0.05-0.2%; after uniform stirring, gradually dripping into the filtrate of step (3) to obtain a synthetic solution of silicon source and template; wherein the mass ratio of the template solution to the filtrate is 1:1-1:2; the template includes but is not limited to hexadecyltrimethylammonium bromide, dodecyldimethylbenzylammonium chloride, octadecyldimethylhydroxyethylammonium nitrate; Step (5): adding an acid solution dropwise to the synthetic solution obtained in step (4) and transferring the solution to a reaction kettle to adjust the pH value of the solution to 10 to obtain a liquid; Step (6) aging the liquid at a temperature of 35° C. to 45° C. for 1 to 5 hours; Step (7): reacting the aged liquid at a hydrothermal reaction temperature of 100° C. to 130° C. for 3 to 72 hours to obtain a reactant; Step (8): filtering the reactant obtained in step (7) by pressure filtration or suction filtration to obtain a powdery product; Step (9): washing the powdered product with water until the pH reaches 7; Step (10): drying the neutral powder product, with the drying temperature set between 50° C. and 100° C. and the drying time being 1 to 24 hours; Step (11): heating the dried product to 500° C.-600° C. in an air atmosphere for 1-8 hours to remove the template, thereby obtaining a silica molecular sieve; The characteristic parameters of silica molecular sieve are: specific surface area of ​​400-500cm2 g-1 and average pore size of 4.5-5.0nm.

6. The method for preparing a sodium ion battery silicon dioxide molecular sieve composite negative electrode sheet according to claim 5, characterized in that: The specific process of step 12 is as follows: Step (1) dissolving the adhesive in a solvent to obtain a first slurry, wherein the mass ratio of the adhesive to the solvent is 1:1-1:9; Step (2) dispersing the silica molecular sieve in solvent NMP, with the mass ratio of silica molecular sieve to solvent NMP being 1:1-1:5, to prepare a second slurry; Step (3) mixing the first slurry and the second slurry in a mass ratio of 1:1-1:2 and stirring for 1-24 hours to form a mixed slurry to obtain a silica molecular sieve composite slurry; The viscosity of the silicon dioxide molecular sieve composite slurry is 100-1000 CPS; the stirring temperature is controlled at RT-140° C. according to the process, and electric heating is adopted.

7. The method for preparing a sodium ion battery silicon dioxide molecular sieve composite negative electrode sheet according to claim 6, characterized in that: The step 13 is specifically as follows: The silica molecular sieve composite slurry and the coal gasification slag-based sodium ion battery soft carbon negative electrode material described in step 10 are coated. The coal gasification slag-based sodium ion battery soft carbon negative electrode material is first coated on an aluminum foil or copper foil substrate, and then the silica molecular sieve composite slurry is coated after drying to prepare a gasification slag-based soft carbon negative electrode material surface composite silica molecular sieve electrode sheet.

8. The method for preparing a sodium ion battery silicon dioxide molecular sieve composite negative electrode sheet according to claim 7, characterized in that: The composite electrode coating process is: unwinding, preheating, coating, baking, and winding; the specific steps are as follows: Step (1) placing the copper foil or aluminum foil substrate on the unwinding device, automatically correcting the deviation, and entering the unwinding tension system; Step (2) After adjusting the unwinding tension, enter the preheating oven for preheating; the preheating temperature is 60-80 degrees; Step (3) The substrate arrives at the coating head, and the composite electrode is coated according to the set program of the coating system; Step (4) The coated wet electrode piece enters an oven and is dried by hot air; Step (5) The tension of the dried composite electrode is adjusted by the tension system, and the winding speed is controlled to be synchronized with the coating speed; Step (6) the composite electrode is automatically corrected by the correction system so that it remains in the set position and is reeled up by the reeling device; Wherein, the thickness of the copper foil or aluminum foil substrate in step (1) is 7-20 μm; In the composite electrode of step (6), the wet thickness of the silicon dioxide molecular sieve coating is: (2-13) μm (single-sided wet thickness); double-sided coating is adopted; Silica molecular sieve coating dry thickness: (1-4) μm (single-sided dry thickness); double-sided coating is adopted; The coating dry thickness of the gasification slag-based soft carbon negative electrode material is 50 to 300 um; The thickness ratio of the gasification slag-based soft carbon negative electrode material and the silicon dioxide molecular sieve coating is 20:1-5:1; The coating method adopted in step (4) is: slot extrusion coating; The preheating and baking temperature in step (4) is 50-140 degrees.

9. A sodium ion battery silicon dioxide molecular sieve composite negative electrode plate, characterized in that: The surface layer is a silicon dioxide molecular sieve, the middle layer is a coal-based gasification slag soft carbon negative electrode material, and the bottom layer is an aluminum conductive substrate; the surface of the coal-based gasification slag soft carbon negative electrode material is a uniform solid electrolyte interface rich in inorganic substances; The silicon dioxide molecular sieve is a long-range ordered mesoporous material with a specific surface area of ​​400 to 500 m 2 / g, pore volume 0.4-0.6cm3 / g, molecular sieve particle size is 150-200nm, its pores are arranged in hexagonal order, and the pore diameter is 4-5nm.

10. An application of a sodium ion battery silicon dioxide molecular sieve composite negative electrode plate, characterized in that: The sodium ion battery silica molecular sieve composite negative electrode plate is applied to the negative electrode of the sodium ion battery cell, and the negative electrode of the sodium ion battery cell includes a cylindrical sodium ion battery cell negative electrode, a square shell sodium ion battery cell negative electrode or a soft package sodium ion battery cell negative electrode; after the series of battery cells are manufactured, modules and PACKs are performed to combine into battery packs and energy management systems, which are used for large-scale energy storage, industrial and commercial energy storage, distributed energy storage or power battery systems.

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