Preparation method of coal gasification slag-based sodium ion battery soft carbon negative electrode material

Abstract

The invention discloses a preparation method of a soft carbon negative electrode material of a coal gasification slag-based sodium ion battery. The preparation method comprises the following steps: step 1, grinding selected gasification slag; 2, the gasified slag is subjected to physical flotation; 3, low-ash and high-carbon gasification slag is subjected to pre-oxidation treatment; step 4, carrying out coarse grinding on the pre-oxidized low-ash and high-carbon gasification slag; 5, the gasified slag obtained after coarse grinding is subjected to fine grinding; 6, the gasified slag obtained after fine grinding is subjected to particle size matching; 7, the gasified slag obtained after particle size matching is subjected to hydrochloric acid pickling; 8, the gasified slag obtained after acid pickling is subjected to NaOH alkali washing; 9, treating the gasified slag subjected to alkali washing with hydrofluoric acid; and step 10, carrying out secondary pre-oxidation on the gasification slag to obtain the soft carbon negative electrode material of the coal gasification slag-based sodium-ion battery. The lithium ion battery has the characteristics of large first discharge capacity, large reversible capacity, long cycle life, good safety and good high-rate performance.

Description

Technical Field

[0001] The invention relates to the technical field of carbon negative electrode materials, and in particular to a method for preparing a coal gasification slag-based sodium battery soft carbon negative electrode material. Background Art

[0002] As a world-class base for methanol and coal-to-liquids, my country produces nearly 100 million tons of coal gasification slag every year. Currently, only a small amount is used for cement blending. Most of the slag is disposed of by landfill or open-air dumping, occupying a large amount of land and seriously polluting the local environment. In addition, the processing cost is very high (30-70 yuan / ton), which seriously increases the production and operation costs of enterprises.

[0003] Coal gasification slag mainly comes from the incomplete combustion process of coal, contains a large amount of residual carbon (10-60%), and has the advantages of high specific surface area, high conductivity, and high chemical stability. Therefore, it is considered to be a potential and competitive sodium battery negative electrode material.

[0004] The bottleneck of the sodium battery industry chain comes from the negative electrode. The types of negative electrodes and their existing problems are as follows:

[0005] 1. Resin-based carbon negative electrodes have the highest specific capacity and are most suitable for controlled synthesis, but their cost is extremely high and large-scale production is difficult.

[0006] 2. The indicators of biomass-based carbon anode are excellent, but the difficulty is that it is affected by the characteristics of biological sources, the batch stability is poor, and it is difficult to scale up;

[0007] 3. Anthracite has a lower cost and the highest carbon yield; the patent application document with application number 202111673684.8 discloses a coal-based negative electrode material and its preparation method and application, in which volatile organic matter is fully mixed with pretreated coal powder, subjected to low-temperature heat treatment, and then subjected to high-temperature heat treatment to obtain a hard carbon material as a negative electrode material for sodium ion batteries. However, the coal-based hard carbon negative electrode material prepared by this process has problems from a performance perspective: low capacity, low initial efficiency, short cycle life, low rate, and prominent dendrite problems; the investment problem is: large investment in high and low temperature carbonization equipment; the problem from a cost perspective is: large equipment investment, high temperature process, and high energy consumption, resulting in high cost and low competitiveness.

[0008] The patent application document with application number 202111478021.0 discloses a soft and hard carbon composite negative electrode material for sodium ion batteries and its preparation method. After anthracite is micro-oxidized and sintered with organic matter for carbonization, the obtained soft and hard carbon composite negative electrode material can further improve the conductivity of the material and improve the rate performance of the material. However, although the rate performance of the coal-based soft and hard carbon composite negative electrode material prepared by this process has been improved, the capacity, first efficiency, and cycle life are still very low, and the dendrite problem has not been solved; the process still requires large equipment investment; it still requires high and low temperature two-step carbonization, which has high temperature, high energy consumption, high cost, and low competitiveness.

[0009] 4. The composition and structure of asphalt are highly controllable, the carbon yield is high, and the conductivity is good. However, during production, it undergoes a liquid-solid two-phase process, which easily generates glassy carbon and graphite. Summary of the invention

[0010] In order to overcome the defects of the above-mentioned prior art, the purpose of the present invention is to provide a method for preparing a coal gasification slag-based sodium ion battery soft carbon negative electrode material. By means of physical flotation, the carbon content is greatly increased. The prepared coal gasification slag-based sodium ion battery soft carbon negative electrode material has the characteristics of large first discharge capacity and large reversible capacity.

[0011] In order to achieve the above object, the technical solution adopted by the present invention is:

[0012] A method for preparing a coal gasification slag-based sodium battery soft carbon negative electrode material comprises the following steps:

[0013] Step 1: Select gasification slag from the gasification process of methanol and coal-to-liquid production, and pre-grind the selected gasification slag;

[0014] Step 2: Physically flotation the pre-ground fumed slag in step 1 to obtain low-ash, high-carbon fumed slag;

[0015] Step 3: pre-oxidizing the low-ash, high-carbon gasified slag;

[0016] Step 4: coarsely grinding the low-ash, high-carbon gasified slag after pre-oxidation in step 3;

[0017] Step 5: finely grinding the gasified slag after the coarse grinding in step 4;

[0018] Step 6: The gasified slag after fine grinding in step 5 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;

[0019] Step 7: washing the gasified slag after the particle size ratio in step 6 with hydrochloric acid;

[0020] Step 8: performing NaOH alkaline washing on the gasified slag which has been pickled with hydrochloric acid in step 7;

[0021] Step 9: treating the gasified slag washed with NaOH in step 8 with hydrofluoric acid;

[0022] Step 10: Perform secondary pre-oxidation on the gasified slag treated in step 9 to obtain a coal gasification slag-based sodium ion battery soft carbon negative electrode material.

[0023] In the step 1, the selected gasified slags are coarse gasified slag and fine gasified slag, the carbon content of the coarse gasified slag is 5%-25%, and the carbon content of the fine gasified slag is 15-50%;

[0024] 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.

[0025] In step 2, the specific steps of physical flotation include: vibration screening, heavy medium flotation, and filter pressing;

[0026] Vibration screening reduces the particle size to between 125-500 microns, with a specific surface area greater than 200m 2 ·g -1 The gasified slag is screened out, and the carbon content of the gasified slag in this range is relatively high; it is used as a precursor raw material for sodium ion negative electrode materials;

[0027] The gasified slag after vibration screening is subjected to heavy medium flotation, and the gasified slag is separated according to its density by using a cyclone. 3 The low-ash, high-carbon gasified slag is separated;

[0028] The gasified slag after heavy medium flotation is filtered; a plate filter press is used to remove the main free water.

[0029] The particle size of the gasified slag obtained by physical flotation is 120-500 microns, and the specific surface area is greater than 200m 2 ·g -1 , 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%.

[0030] The step 3 is specifically as follows:

[0031] The 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 0.5-5 hours.

[0032] The pre-oxidation equipment is limited to rotary kiln pre-oxidation equipment, and the pre-oxidation equipment adopts external heating or internal heating.

[0033] The step 4 is specifically as follows:

[0034] The low-ash, high-carbon gasified slag after pre-oxidation is crushed to a particle size of 50-100 microns.

[0035] The coarse grinding equipment adopts a hammer crusher, but is not limited to a hammer crusher.

[0036] The step 5 is specifically as follows:

[0037] Grind the low-ash, high-carbon gasified slag with a particle size of 50-100 microns into 1-20 microns;

[0038] The low-ash, high-carbon gasified slag above 20 microns is returned for further grinding;

[0039] The fine grinding equipment adopts Raymond mill crusher, but is not limited to Raymond mill crusher.

[0040] The particle size of step 6 is proportioned in the following manner:

[0041] D10 is 1 micron; D50 is 5 microns; D90 is 15 microns; D100 is 20 microns.

[0042] The step 7 is specifically as follows:

[0043] The treatment is carried out with 10-30wt% hydrochloric acid for 4-8h at a temperature of 30-80°C, wherein the solid-liquid mass ratio of the fumed slag to the hydrochloric acid solution is 1:3-1:10. The purpose of this step is to wash away all the basic oxides in the fumed slag, such as aluminum oxide, iron oxide, calcium oxide, magnesium oxide, etc.

[0044] The step 8 is specifically as follows:

[0045] 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 mass ratio of gasified slag to sodium hydroxide solution is 1:5-1:15; wash away all acidic oxides in the gasified slag, such as silicon dioxide.

[0046] The step 9 is specifically as follows:

[0047] Hydrofluoric acid with a mass concentration of 1-10wt% is selected for treatment, the treatment time is 2-6h, the treatment temperature is 60-80°C, and the solid-liquid mass ratio of gasified slag to hydrofluoric acid solution is 1:1-1:2.

[0048] The step 10 is specifically as follows:

[0049] The gasified slag after acid and alkali washing is subjected to secondary pre-oxidation at a temperature of 100-500°C;

[0050] The oxygen-containing functional groups introduced by pre-oxidation increase the active sites for sodium ion storage. The carbonyl functional groups generated during the pre-oxidation process undergo cross-linking with the carboxyl groups to undergo esterification reactions, increasing the disorder of the carbon structure, thereby obtaining a soft carbon negative electrode material for sodium ion batteries based on coal gasification slag and improving the sodium storage performance of the material.

[0051] The equipment for secondary pre-oxidation is not limited to rotary kiln, and internal heating equipment or external heating equipment may also be used.

[0052] The coal gasification slag-based sodium ion battery soft carbon negative electrode material has a large number of short-range ordered graphite-like stripe domains inside the small particles under transmission electron microscopy, which is a characteristic of the crystal structure of soft carbon materials.

[0053] The particle size of coal gasification slag-based sodium ion battery soft carbon negative electrode material is 1-20 microns;

[0054] The soft carbon negative electrode material of coal gasification slag-based sodium ion battery has a three-dimensional mesoporous structure with a pore size between 1 and 50 nanometers, with 2 to 10 nanometers accounting for more than 80%;

[0055] The particle size of the coal gasification slag-based sodium-ion battery soft carbon negative electrode material is 1-20 microns, but is not limited to 1-20 microns.

[0056] Beneficial effects of the present invention:

[0057] The coal gasification slag-based sodium-ion battery soft carbon negative electrode material undergoes two pre-oxidation steps to introduce oxygen-containing functional groups, and by introducing CO single-bond functional groups, the sodium ion charge and discharge capacity is increased.

[0058] Physical flotation effect: low-cost physical flotation of gasified slag can significantly increase the carbon content to more than 85% and significantly reduce impurities to less than 15%;

[0059] Particle size advantage: The particle size of the gasified slag after coarse and fine grinding can be matched to produce sodium battery negative electrode materials with high real density and tap density; shorten the grinding process and investment; and greatly improve production efficiency;

[0060] Acid-base washing purification effect: After acid-base washing of gasified slag, the carbon content is further increased to more than 90%, and the impurity content is reduced to less than 0.3%;

[0061] Process investment effect: The gasified slag has undergone a high-temperature gasification process of 1250-1300℃, so there is no need for subsequent high-temperature carbonization. There is no need to invest in low-temperature pre-carbonization equipment and high-temperature carbonization equipment, which greatly reduces the investment amount;

[0062] Cost effect: large quantity and wide range, rich resources, basically zero raw material cost, low subsequent manufacturing cost, and strong competitive advantage;

[0063] Capacity advantage: gasification slag has a high surface area and high porosity, and the first discharge capacity is very high, which can greatly increase the capacity; the coal gasification slag-based sodium ion battery soft carbon negative electrode material prepared by the present invention has a first discharge capacity of more than 500mAh / g and a reversible capacity of more than 260mAh / g;

[0064] High rate performance effect; the discharge curve slope capacity is greater than 200mAh / g. At a 4C charge and discharge rate, the performance is more than 5 times the capacity of organic precursors such as coconut shell and asphalt;

[0065] Cycle life advantage: The pore size of gasified slag is mesoporous (5-10 nanometer pores account for more than 90%), which is conducive to the entry and exit of sodium ions, thereby increasing the cycle life of sodium batteries and reducing attenuation; the cycle life of gasified slag is expected to reach more than 6,000 times;

[0066] Safety effect: The prepared coal gasification slag negative electrode material has a reversible capacity of more than 260mAh / g, of which the discharge curve slope capacity is more than 200mAh / g, and the capacity below 0.1V is low, which greatly reduces the generation of dendrites and greatly improves the safety of sodium batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 It is a schematic diagram of the pore size distribution of the gasified slag of the present invention.

[0068] Figure 2 This is the infrared spectrum of gasified slag.

[0069] Figure 3 This is the first charge and discharge curve of the coal gasification slag-based sodium soft carbon negative electrode manufactured by the present invention.

[0070] Figure 4 It is the rate performance diagram.

[0071] Figure 5 This is a comparison of the charge and discharge curves of three carbon negative electrodes at 4C rate.

[0072] Figure 6 This is a cycle performance diagram of the coal gasification slag-based sodium soft carbon negative electrode manufactured by the present invention.

[0073] Figure 7 This is a scanning electron microscope image of the coal gasification slag-based sodium battery soft carbon negative electrode material manufactured in Example 1.

[0074] Figure 8 This is a transmission electron microscope image of coal gasification slag-based sodium battery soft carbon negative electrode material. DETAILED DESCRIPTION

[0075] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0076] A method for preparing a coal gasification slag-based sodium ion battery soft carbon negative electrode material comprises the following steps:

[0077] The chemical composition of the selected coal gasification slag is shown in Table 1:

[0078] Table 1 Chemical composition of a selected gasified slag

[0079] Element <![CDATA[SiO 2 ]]> <![CDATA[Al 2 THE 3 ]]> <![CDATA[Fe 2 THE 3 ]]> CaO MgO <![CDATA[Na 2 The]]> <![CDATA[K 2 The]]> <![CDATA[P 2 THE 5 ]]> <![CDATA[TiO 2 ]]> <![CDATA[SO 3 ]]> content 39.24 13.82 3.22 3.42 0.31 0.36 0.91 0.05 1.08 1.28

[0080] As can be seen from Table 1, the main components of coal gasification slag are SiO 2 、Al 2 O 3 , Fe 2 O 3 , CaO, residual carbon, and some small amounts of MgO, Na 2 O.K 2 O.P 2 O 5 、TiO 2 、SO 3 wait;

[0081] The average particle sizes of the selected gasified slag are: D20: 24.52 microns, D25: 31.11 microns, D50: 78.26 microns, D75: 142.71 microns, and D95: 273.28 microns.

[0082] The pore structure and specific surface area of ​​the selected gasified slag are shown in Table 2:

[0083] Table 2: Pore structure and specific surface area parameters of a selected gasification slag

[0084]

[0085] As can be seen from Table 2, the specific surface area of ​​coal gasification furnace slag is large and the average pore size is small;

[0086] The pore size of gasified slag is all mesoporous (90% of the pores are 5-10 nanometers), which is conducive to the entry and exit of sodium ions, thereby increasing the cycle life of sodium batteries and reducing attenuation.

[0087] The infrared spectrum analysis of the functional groups and carbon-oxygen bond structure of a selected gasified slag is as follows: Figure 2 As shown;

[0088] The infrared spectrum of gasified slag is at 3440cm -1 and 1061cm -1 There are two obvious absorption peaks of hydroxyl -OH, indicating that the coal gasification slag has strong hydrophilicity, 1638cm -1 The carbonyl C=O absorption peak may appear nearby, 700-900cm -1The absorption peak of aromatic CH or benzene ring is 400-550cm -1 It is the absorption peak of minerals.

[0089] From the infrared spectrum analysis of gasified slag, we can know that the surface of gasified slag contains a large number of oxygen-containing surface functional groups and a certain aromatic core structure, which creates a good raw material basis for subsequent modification.

[0090] The charge and discharge curves of the soft carbon negative electrode of coal gasification slag-based sodium ion battery are shown in Figure 2. Figure 3 As shown; the first charge specific capacity is 500mAh / g, the discharge specific capacity is 260mAh / g, and the slope area specific capacity reaches more than 200mAh / g;

[0091] The rate performance of coal gasification slag-based soft carbon anode for sodium ion batteries Figure 4 As shown;

[0092] At a charge-discharge rate of 4C, the charge-discharge curves of the coal gasification slag-based soft carbon anode and the coconut shell and asphalt-derived carbon anode are as follows: Figure 5 As shown in the figure, the reversible specific capacity of the coal gasification slag-based soft carbon negative electrode is 3-5 times that of other carbon materials.

[0093] The cycle life of gasified slag reaches more than 6000 times; Figure 6 As shown;

[0094] Scanning electron microscope image of coal gasification slag-based soft carbon negative electrode material for sodium ion battery Figure 7 As shown; the surface particles are rough, with a large number of small-sized particles adhering to its surface, and some filling the pores.

[0095] Transmission electron microscope photo of coal gasification slag-based soft carbon negative electrode material for sodium ion battery Figure 8 As shown in the figure, there are many short-range ordered graphite-like stripe domains inside the small particles, which are typical crystal structure characteristics of soft carbon materials.

[0096] Embodiment 1:

[0097] 1) Selecting coarse slag and fine slag of gasification slag in the gasification process of methanol manufacturing, the ratio of coarse slag to fine slag is 50% each; the carbon content of the coarse slag is 29.95%, and the carbon content of the fine gasification slag is 40.13%; the particle size of the mixed gasification slag is 100 microns-1300 microns;

[0098] 2) After vibration screening, the gasified slag with a size of more than 500 microns and an ash content of more than 96.02% is selected for other uses; the gasified slag with a size of less than 500 microns enters the subsequent heavy medium flotation process;

[0099] 3) Through heavy medium flotation, the cyclone density range is 1.10-1.30g / cm 3 High carbon and low ash gasification slag; specific surface area is 210m2 ·g -1 ;

[0100] 4) The high-carbon and low-ash gasified slag from physical flotation was filtered by a plate filter press to remove free water, and the mesoporous gasified slag still adsorbed 61% of water;

[0101] 5) The carbon content of the gasified slag obtained by physical flotation is 84.56%;

[0102] 6) The high-carbon and low-ash gasified slag obtained through physical flotation is pre-oxidized in a rotary kiln at a temperature of 300 degrees and direct heating is used for pre-oxidation; the pre-oxidation time is 3 hours, and the CO functional group content after pre-oxidation is 5%;

[0103] 7) Rough crushing is carried out in a hammer crusher, and the particle size of the rough grinding is crushed from the original 100-500 microns to less than 100 microns;

[0104] 8) Fine grinding is performed by Raymond mill, and the particle size of the gasified slag produced by fine grinding is 1-20 microns;

[0105] 9) Screening the finely ground gasified slag into several grades: less than 1 micron, less than 5 microns, less than 15 microns, less than 20 microns, and more than 20 microns; the gasified slag with a diameter of more than 20 microns is returned for further fine grinding;

[0106] 10) Proportioning is performed, and the proportions are: D10 is 1 micron; D50 is 5 microns; D90 is 15 microns; D100 is 20 microns.

[0107] 11) Pickling the fumed slag after particle size classification, with a hydrochloric acid concentration of 10%wt, a reaction temperature of 80°C, a reaction time of 8 hours, and a solid-liquid ratio of the fumed slag to the hydrochloric acid solution of 1:3; washing away all alkaline oxides in the fumed slag, such as aluminum oxide, iron oxide, calcium oxide, magnesium oxide, etc.;

[0108] 12) The acid-washed fumed slag is washed with 3%wt NaOH for 10h at a temperature of 90°C and a solid-liquid ratio of 1:5 between the fumed slag and the sodium hydroxide solution to remove all acidic oxides in the fumed slag, such as silicon dioxide;

[0109] 13) treating the treated gasified fine slag with hydrofluoric acid having a mass concentration of 1%wt for 6 hours at a temperature of 80°C, with a solid-liquid mass ratio of the gasified slag to the hydrofluoric acid solution of 1:1;

[0110] 14) The gasified slag after acid and alkali washing is subjected to secondary pre-oxidation in a rotary kiln. The secondary pre-oxidation adopts internal direct heating, the pre-oxidation temperature is 300° C., the pre-oxidation time is 3 hours, and the CO functional group content after two pre-oxidations is 11%;

[0111] Through the above treatment, the core indicators of a coal gasification slag-based sodium ion battery soft carbon negative electrode material prepared are:

[0112] The carbon content is 93%; the ash content is less than 0.26%; the CO content is 11%; the pore size is between 1-50 nanometers, of which 2-10 nanometers accounts for 81%; and the mesopores are distributed in a three-dimensional space.

[0113] Embodiment 2:

[0114] 1) Selecting coarse slag and fine slag of gasification slag in the gasification process of methanol manufacturing, the ratio of coarse slag to fine slag is 40%:60%; the carbon content of the coarse slag is 20.32%, and the carbon content of the fine gasification slag is 30.17%; the particle size of the mixed gasification slag is 100 microns-1300 microns;

[0115] 2) After vibration screening, the gasified slag with a size of more than 500 microns and an ash content of more than 96.02% is selected for other uses; the gasified slag with a size of less than 500 microns enters the subsequent heavy medium flotation process;

[0116] 3) Through heavy medium flotation, the cyclone density range is 1.10-1.30g / cm 3 High carbon and low ash gasification slag; specific surface area is 227m 2 ·g -1 ;

[0117] 4) The high-carbon and low-ash gasified slag from physical flotation was filtered by a plate filter press to remove free water, and the mesoporous gasified slag still adsorbed 58% of water;

[0118] 5) The carbon content of the gasified slag obtained by physical flotation is 88.31%;

[0119] 6) The high-carbon and low-ash gasified slag obtained through physical flotation is pre-oxidized in a rotary kiln at a temperature of 350 degrees and direct heating is used for pre-oxidation; the pre-oxidation time is 2 hours, and the CO functional group content after pre-oxidation is 6%;

[0120] 7) Rough crushing is carried out in a hammer crusher, and the particle size of the rough grinding is crushed from the original 100-500 microns to less than 100 microns;

[0121] 8) Fine grinding is performed by Raymond mill, and the particle size of the gasified slag produced by fine grinding is 1-20 microns;

[0122] 9) Screening the finely ground gasified slag into several grades: less than 1 micron, less than 5 microns, less than 15 microns, less than 20 microns, and more than 20 microns; the gasified slag with a diameter of more than 20 microns is returned for further fine grinding;

[0123] 10) Proportioning is performed, and the proportions are: D10 is 1 micron; D50 is 5 microns; D90 is 15 microns; D100 is 20 microns.

[0124] 11) Pickling the fumed slag after particle size classification, with a hydrochloric acid concentration of 20%wt, a reaction temperature of 50°C, a reaction time of 6 hours, and a solid-liquid ratio of the fumed slag to the hydrochloric acid solution of 1:6; washing away all alkaline oxides in the fumed slag, such as aluminum oxide, iron oxide, calcium oxide, magnesium oxide, etc.;

[0125] 12) The acid-washed fumed slag is washed with 4%wt NaOH for 10h at a temperature of 80°C and a solid-liquid ratio of 1:10 to remove all acidic oxides in the fumed slag, such as silicon dioxide;

[0126] 13) treating the treated gasified fine slag with hydrofluoric acid having a mass concentration of 2%wt for 5 hours at a temperature of 70°C, with a solid-liquid mass ratio of the gasified slag to the hydrofluoric acid solution of 1:2;

[0127] 14) The gasified slag after acid and alkali washing is subjected to secondary pre-oxidation in a rotary kiln. The secondary pre-oxidation adopts internal direct heating, the pre-oxidation temperature is 350° C., the pre-oxidation time is 2 hours, and the CO functional group content after two pre-oxidations is 12%;

[0128] Through the above treatment, the core indicators of a coal gasification slag-based sodium ion battery soft carbon negative electrode material prepared are:

[0129] The carbon content is 94%; the ash content is less than 0.25%; the CO content is 12%; the pore size is between 1-50 nanometers, of which 2-10 nanometers accounts for 83%; and the mesopores are distributed in a three-dimensional space.

[0130] Embodiment 3:

[0131] 1) Selecting coarse slag and fine slag of gasification slag in the gasification process of methanol manufacturing, the ratio of coarse slag to fine slag is 30%:70%; the carbon content of the coarse slag is 15.32%, and the carbon content of the fine gasification slag is 35.30%; the particle size of the mixed gasification slag is 100 microns-1300 microns;

[0132] 2) After vibration screening, the gasified slag with a size of more than 500 microns and an ash content of more than 96.02% is selected for other uses; the gasified slag with a size of less than 500 microns enters the subsequent heavy medium flotation process;

[0133] 3) Through heavy medium flotation, the cyclone density range is 1.10-1.30g / cm 3 High carbon and low ash gasified slag; specific surface area is 231m 2 ·g -1 ;

[0134] 4) The high-carbon and low-ash gasified slag from physical flotation was filtered by a plate filter press to remove free water, and the mesoporous gasified slag still adsorbed 54% of water;

[0135] 5) The carbon content of the gasified slag obtained by physical flotation is 89.61%;

[0136] 6) The high-carbon and low-ash gasified slag obtained through physical flotation is pre-oxidized in a rotary kiln at a temperature of 380 degrees and direct heating is used for pre-oxidation; the pre-oxidation time is 1 hour, and the CO functional group content after pre-oxidation is 7%;

[0137] 7) Rough crushing is carried out in a hammer crusher, and the particle size of the rough grinding is crushed from the original 100-500 microns to less than 100 microns;

[0138] 8) Fine grinding is performed by Raymond mill, and the particle size of the gasified slag produced by fine grinding is 1-20 microns;

[0139] 9) Screening the finely ground gasified slag into several grades: less than 1 micron, less than 5 microns, less than 15 microns, less than 20 microns, and more than 20 microns; the gasified slag with a diameter of more than 20 microns is returned for further fine grinding;

[0140] 10) Proportioning is performed, and the proportions are: D10 is 1 micron; D50 is 5 microns; D90 is 15 microns; D100 is 20 microns.

[0141] 11) Pickling the fumed slag after particle size classification, with a hydrochloric acid concentration of 30%wt, a reaction temperature of 30°C, a reaction time of 4 hours, and a solid-liquid ratio of the fumed slag to the hydrochloric acid solution of 1:10; washing away all alkaline oxides in the fumed slag, such as aluminum oxide, iron oxide, calcium oxide, magnesium oxide, etc.;

[0142] 12) The acid-washed fumed slag is washed with 5%wt NaOH for 6 hours at a temperature of 60°C and a solid-liquid ratio of 1:15 between the fumed slag and the sodium hydroxide solution to remove all acidic oxides in the fumed slag, such as silicon dioxide;

[0143] 13) treating the gasified fine slag treated with hydrochloric acid with a mass concentration of 3% wt of hydrofluoric acid for 2 hours at a temperature of 60° C. The solid-liquid mass ratio of the gasified slag to the hydrofluoric acid solution is 1:2;

[0144] 14) The gasified slag after acid and alkali washing is subjected to secondary pre-oxidation in a rotary kiln. The secondary pre-oxidation adopts internal direct heating, the pre-oxidation temperature is 380 degrees, the pre-oxidation time is 1 hour, and the CO functional group content after two pre-oxidations is 13%;

[0145] Through the above treatment, the core indicators of a coal gasification slag-based sodium ion battery soft carbon negative electrode material prepared are:

[0146] The carbon content is 96%; the ash content is less than 0.21%; the CO content is 13%; the pore size is between 1-50 nanometers, of which the proportion of 2-10 nanometers is 86%; the mesopores are distributed in a three-dimensional space.

Claims

1. A method for preparing a soft carbon negative electrode material for a coal gasification slag-based sodium battery, characterized in that: The following steps are involved: Step 1: Select gasification slag from the gasification process of methanol and coal-to-liquid production, and pre-grind the selected gasification slag; Step 2: Physically flotation the pre-ground fumed slag in step 1 to obtain low-ash, high-carbon fumed slag; Step 3: pre-oxidizing the low-ash, high-carbon gasified slag; Step 4: coarsely grinding the low-ash, high-carbon gasified slag after pre-oxidation in step 3; Step 5: finely grinding the gasified slag after the coarse grinding in step 4; Step 6: performing particle size matching on the gasified slag finely ground in step 5; Step 7: washing the gasified slag after the particle size ratio in step 6 with hydrochloric acid; Step 8: performing NaOH alkaline washing on the gasified slag which has been pickled with hydrochloric acid in step 7; Step 9: treating the gasified slag washed with NaOH in step 8 with hydrofluoric acid; Step 10: Perform secondary pre-oxidation on the gasified slag treated in step 9 to obtain a coal gasification slag-based sodium ion battery soft carbon negative electrode material.

2. The method for preparing a coal gasification slag-based sodium battery soft carbon negative electrode material according to claim 1, characterized in that: In the step 1, the selected gasified slags are coarse gasified slag and fine gasified slag, the carbon content of the coarse gasified slag is 5%-25%, and the carbon content of the fine gasified slag is 15-50%; The coarse gasified slag and the fine gasified slag are mixed in any proportion, and the mineral particle size of the gasified slag is between 10 and 350 microns.

3. The method for preparing a coal gasification slag-based sodium battery soft carbon negative electrode material according to claim 1, characterized in that: In step 2, the specific steps of physical flotation include: vibration screening, heavy medium flotation, and filter pressing; Vibration screening reduces the particle size to between 125-500 microns, with a specific surface area greater than 200m 2 ·g -1 The gasified slag is screened out; The gasified slag after vibration screening is subjected to heavy medium flotation, and the gasified slag is separated according to its density by using a cyclone. 3 The low-ash, high-carbon gasified slag is separated; The gasified slag after heavy medium flotation is subjected to filter pressing; The particle size of the gasified slag obtained by physical flotation is 120-500 microns, and the specific surface area is greater than 200m 2 ·g -1 , 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%.

4. The method for preparing a coal gasification slag-based sodium battery soft carbon negative electrode material according to claim 1, characterized in that: The step 3 is specifically as follows: Pre-oxidation equipment is used to pre-oxidize the low-ash, high-carbon gasified slag, the pre-oxidation temperature is 100-500° C., and the pre-oxidation time is 0.5-5 hours; The pre-oxidation equipment is limited to rotary kiln pre-oxidation equipment, and the pre-oxidation equipment adopts external heating or internal heating; The step 4 is specifically as follows: Crushing the pre-oxidized low-ash, high-carbon gasified slag to a particle size of 50-100 microns; The coarse grinding equipment adopts a hammer crusher, but is not limited to a hammer crusher.

5. The method for preparing a coal gasification slag-based sodium battery soft carbon negative electrode material according to claim 1, characterized in that: The step 5 is specifically as follows: Grind the low-ash, high-carbon gasified slag with a particle size of 50-100 microns into 1-20 microns; The low-ash, high-carbon gasified slag above 20 microns is returned for further grinding; The fine grinding equipment adopts Raymond mill crusher, but is not limited to Raymond mill crusher.

6. The method for preparing a coal gasification slag-based sodium battery soft carbon negative electrode material according to claim 1, characterized in that: 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.

7. The method for preparing a coal gasification slag-based sodium battery soft carbon negative electrode material according to claim 1, characterized in that: The step 7 is specifically as follows: Select 10-30wt% hydrochloric acid for treatment, the treatment time is 4-8h, the treatment temperature is 30-80°C, wherein the solid-liquid mass ratio of the gasified slag to the hydrochloric acid solution is 1:3-1:

10.

8. The method for preparing a coal gasification slag-based sodium battery soft carbon negative electrode material according to claim 1, characterized in that: 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 mass ratio of gasified slag to sodium hydroxide solution is 1:5-1:15; The step 9 is specifically as follows: Hydrofluoric acid with a mass concentration of 1-10wt% is selected for treatment, the treatment time is 2-6h, the treatment temperature is 60-80°C, and the solid-liquid mass ratio of gasified slag to hydrofluoric acid solution is 1:1-1:

2.

9. The method for preparing a coal gasification slag-based sodium battery soft carbon negative electrode material according to claim 1, characterized in that: 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; The oxygen-containing functional groups introduced by pre-oxidation increase the active sites for sodium ion storage. The carbonyl functional groups generated during the pre-oxidation process undergo cross-linking with the carboxyl groups to undergo esterification reactions, increasing the disorder of the carbon structure and obtaining coal gasification slag-based sodium ion battery soft carbon negative electrode materials. The equipment for secondary pre-oxidation is not limited to rotary kiln, and internal heating equipment or external heating equipment may also be used.

10. The coal gasification slag-based sodium battery soft carbon negative electrode material prepared according to any one of claims 1 to 9, characterized in that: The coal gasification slag-based sodium ion battery soft carbon negative electrode material has a large number of short-range ordered graphite-like stripe domains inside the small particles under transmission electron microscopy, which is a characteristic of the crystal structure of soft carbon materials. The particle size of coal gasification slag-based sodium ion battery soft carbon negative electrode material is 1-20 microns; The soft carbon negative electrode material of coal gasification slag-based sodium ion battery has a three-dimensional mesoporous structure with a pore size between 1 and 50 nanometers, with 2 to 10 nanometers accounting for more than 80%; The particle size of the coal gasification slag-based soft carbon negative electrode material for sodium-ion batteries is 1-20 microns.

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