Negative electrode material prepared from high-sulfur coal and preparation method of negative electrode material

Abstract

According to the negative electrode material prepared from the high-sulfur coal and the preparation method of the negative electrode material, a composite deliming solution of nitric acid and hydrochloric acid is adopted, the balance effect of the two acids in the composite deliming solution is regulated and controlled through a formula, then the high-sulfur coal material with low ash content and high purity is screened out, and the sodium storage capacity and the electrochemical performance are improved. When the molar ratio of NO3 <-> to Cl <-> in the composite deliming solution, the amount-of-substance concentration of H < + > and the stirring time meet the formula that 1.75-0.65 c-1. 02 alpha + 0.08 c2 + 0.46 alpha 2 + 5.43 e-0. 735 t is larger than or equal to 0.01 and smaller than or equal to 1, the optimal etching degree of the high-sulfur coal material can be achieved, so that sulfur minerals in the high-sulfur coal material are effectively removed, more sodium storage sites are obtained, and rapid transmission of Na < + > is promoted; and the negative electrode material prepared from the high-sulfur coal has relatively high sodium storage capacity and first coulombic efficiency, so that the electrochemical performance of the battery is improved.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery material preparation, specifically relating to a method for preparing a negative electrode material from high-sulfur coal. Background Technology

[0002] With the continuous growth of global energy demand and the rapid development of renewable energy technologies, the need for efficient and convenient large-scale energy storage systems is becoming increasingly urgent. Lithium-ion batteries, due to their high energy density and long lifespan, have become the preferred power source for portable electronic devices and electric vehicles over the past few decades. However, the uneven distribution and price fluctuations of lithium resources pose challenges to the widespread application of lithium-ion batteries. Sodium resources are abundant and inexpensive, and their chemical properties are similar to lithium, making sodium-ion batteries a promising energy storage technology. Sodium-ion batteries have significant advantages in large-scale energy storage, especially in grid-scale energy storage systems, where cost-effectiveness and resource sustainability are particularly important. In sodium-ion batteries, the anode material is one of the key factors determining battery performance; and hard carbon anode materials, due to their wide availability, numerous active sites, and structural stability, have become a research hotspot.

[0003] Precursors for hard carbon anode materials include asphalt, biomass materials, and synthetic resins. Coal, as a naturally occurring carbon precursor, boasts advantages such as abundant raw material sources, high carbon content, and considerable product yield, making it an ideal choice for hard carbon anode materials. However, the sulfur minerals contained in coal, especially pyrite (FeS2) and sulfate minerals, pose challenges to coal processing and utilization. The presence of sulfur minerals has a significant negative impact on the performance of coal-based anode materials. First, these minerals occupy the sodium storage space of the anode material, leading to a decrease in sodium storage capacity. Second, the presence of sulfur minerals reduces the conductivity of the anode material, affecting the battery's charge and discharge efficiency. Furthermore, sulfur minerals may trigger side reactions during charge and discharge, affecting the battery's cycle stability and safety. These sulfur minerals, such as pyrite (FeS2), undergo complex chemical reactions during combustion, decomposing into a significant component of ash.

[0004] Traditional coal-based descaling methods are ineffective at purifying coal; in particular, FeS2 is trapped by the carbon layer in the coal, making it difficult to react fully with acids, resulting in high ash content. This limits the application of high-sulfur coal in electrochemistry and hinders the development of hard carbon anode materials for sodium-ion batteries. Effectively removing sulfur minerals from coal to obtain purer coal-based materials is crucial for advancing the development of hard carbon anode materials for sodium-ion batteries. This not only improves the sodium storage capacity and conductivity of coal-based anode materials but also reduces production costs, improving the cost-effectiveness of sodium-ion batteries. Therefore, developing new coal-based desulfurization technologies to improve coal purification efficiency is an important research topic in the field of sodium-ion batteries. Summary of the Invention

[0005] This invention addresses the problems in the prior art by disclosing a method for preparing anode materials from high-sulfur coal. The method involves treating the high-sulfur coal material with a composite deashing solution of hydrochloric acid and nitric acid, and controlling the balance between the two acids to achieve effective etching of the high-sulfur coal material. This removes sulfur minerals, reduces ash content, and allows for the selection of low-ash, high-purity high-sulfur coal materials, thereby improving sodium storage capacity and electrochemical performance.

[0006] This invention is achieved through the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing anode materials from high-sulfur coal, the specific steps of which include:

[0008] S1: Prepare a composite deashing solution by adding hydrochloric acid and nitric acid to deionized water;

[0009] S2: After crushing the high-sulfur coal, add it to the composite deashing solution described in S1 and stir to obtain a mixed solution;

[0010] S3: Dilute the mixed solution described in S2 with deionized water and filter it to obtain a filter cake. Dry the filter cake to obtain coal powder.

[0011] S4; The coal powder described in S3 is subjected to pre-carbonization treatment and high-temperature carbonization to obtain anode material prepared from high-sulfur coal;

[0012] Steps S1-S4 satisfy 0.01 ≤ 1.75 - 0.65c - 1.02α + 0.08c 2 +0.46α 2 +5.43e -0.735t ≤1, where 0.5≤α≤2; 2≤c≤6mol / L; t>0; α is the NO3 in the composite deashing solution described in S1. - Cl - The molar ratio, c is the H in the composite deashing solution described in S1. + The molar concentration of the substance, t is the stirring time in S2.

[0013] In the material design scheme of the present invention, high-sulfur coal is treated with the composite deashing solution system of the present invention, which can effectively remove sulfur minerals from the coal. On the one hand, the present invention uses hydrochloric acid and nitric acid to prepare the composite deashing solution, which can achieve the best etching degree for high-sulfur coal materials and better utilize NO3. - The dissolution effect of Cl -The invention possesses strong coordination ability with metal impurity ions. Furthermore, by regulating the balance between the two acids, the invention achieves effective etching of high-sulfur coal materials when the balance meets the aforementioned formula range. This effectively removes encapsulated inorganic impurities, allowing for the selection of high-sulfur coal materials with suitable low ash content and high purity. This results in higher sodium storage sites for the high-sulfur coal materials, improving the sodium storage capacity of the negative electrode materials prepared from high-sulfur coal and achieving better electrochemical performance. Simultaneously, when using the composite deashing solution, appropriate time matching is required to achieve effective etching, ensuring sufficient reaction between the composite deashing solution and the high-sulfur coal to achieve the best desulfurization effect.

[0014] As a further embodiment, the S1 composite deashing solution contains: 0.6 ≤ α ≤ 1.3; 2.5 ≤ c ≤ 3.5 mol / L; 0.01 ≤ 1.75 - 0.65c - 1.02α + 0.08c 2 +0.46α 2 +5.43e -0.735t ≤0.2. When this formula meets this limitation, high-sulfur coal materials with suitable low ash content and high purity can be obtained, further increasing the sodium ion storage sites, increasing the sodium storage capacity of high-sulfur coal anode materials, and further improving electrochemical performance. Furthermore, the α and c values ​​selected within this formula range are beneficial to NO3. - With Cl - The molar ratio and concentration are effectively balanced to fully initiate the reaction and avoid excessive etching of high-sulfur coal by the composite deashing solution, thus ensuring the structural stability of the high-sulfur coal and fully exposing the inorganic minerals in the high-sulfur coal, thereby better utilizing NO3. - The dissolution effect of Cl - It has a strong coordination ability with metal impurity ions, avoiding the problem of excessive defects causing impurity ions to complex and become difficult to remove.

[0015] As a further embodiment, the pH value of the filtrate obtained by diluting and filtering with deionized water in S3 is 6-7. When the pH value of the filtrate obtained by diluting and filtering with deionized water is 6-7, the filtrate is neutral, which is conducive to obtaining more sodium storage sites and improving the sodium storage capacity of the negative electrode material prepared from high-sulfur coal.

[0016] As a further option, the pre-carbonization temperature in S4 is selected from 600≤T≤800℃, and the heating rate is 0.1-10℃ / min.

[0017] As a further option, the high-temperature carbonization temperature in S4 is selected from 1100≤T≤1500℃, and the heating rate is 0.1-10℃ / min. Appropriate carbonization temperature and heating rate can ensure that high-sulfur coal materials form a stable carbon structure during carbonization, while avoiding material sintering and structural damage caused by excessively high temperatures or heating rates.

[0018] As a further option, the high-sulfur coal in S1 includes one or more of bituminous coal, anthracite, and coking coal.

[0019] As a further option, the drying device in S3 is one or more of the following: a blower dryer, a freeze dryer, a vacuum drying oven, a rotary flash dryer, and a hot air circulating drying oven.

[0020] Secondly, the present invention provides a negative electrode material prepared from high-sulfur coal, wherein the negative electrode material is obtained by the preparation method described in the first aspect.

[0021] Thirdly, this invention provides a sodium-ion battery negative electrode sheet prepared from high-sulfur coal. The negative electrode sheet comprises the sodium-ion battery negative electrode material prepared from high-sulfur coal as described in the second aspect of this invention, a conductive agent, and a binder. The high-sulfur coal-based negative electrode sheet provided by this invention possesses excellent sodium storage capacity and more sodium storage sites, enabling the battery to achieve higher capacity and longer cycle life during charge and discharge, exhibiting superior electrochemical performance in sodium-ion batteries.

[0022] This invention does not impose any particular limitation on the type of conductive agent, as long as it enhances the conductivity of the negative electrode and does not adversely affect the performance of the sodium-ion battery negative electrode material prepared from high-sulfur coal. Those skilled in the art can select conductive agents commonly used in the field according to actual needs. As some specific examples, the conductive agent used to prepare the negative electrode sheet can be selected from carbon blacks such as acetylene black and conductive carbon black, conductive polymers such as carbon nanotubes, graphene, graphite, polyaniline, and polythiophene, metal oxide conductive agents such as tin oxide and zinc oxide, and carbon nanofiber conductive agents, etc.

[0023] This invention does not impose any particular limitation on the type of binder, as long as it enhances the adhesion between the particles of the negative electrode active material and does not adversely affect the performance of the sodium-ion battery negative electrode material prepared from high-sulfur coal. Those skilled in the art can select the appropriate binder according to actual needs. As some specific examples, binders used to prepare the negative electrode sheet include polyvinylidene fluoride, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, polyimide, polystyrene sulfonic acid, polyacrylonitrile, polycarbonate, or polyetherimide ketone, etc.

[0024] Fourthly, this invention provides a sodium-ion battery, comprising the negative electrode, positive electrode, separator, and electrolyte described in the third aspect. The sodium-ion battery provided by this invention utilizes a negative electrode material prepared from high-sulfur coal, which not only possesses high energy density but also exhibits good stability during cycling, meeting the high capacity and long lifespan requirements of various electronic devices; it is widely used in portable electronic devices, electric vehicles, energy storage systems, and other applications requiring long-term operation and frequent charge-discharge cycles.

[0025] The features and beneficial effects of this invention are as follows:

[0026] This invention fully utilizes NO3 by employing a specific composite deashing solution of nitric acid and hydrochloric acid and processing conditions. - The dissolution effect and Cl - The coordination ability with metal ions is studied, and the balance between the two acids in the composite deashing solution is regulated by a formula. When the formula range is met, the inorganic minerals in high-sulfur coal are fully exposed, achieving effective etching, obtaining more sodium storage sites, thereby reducing ash content and broadening the sodium storage capacity. + The transmission path promotes Na + Rapid transmission; screening out low-ash, high-purity, high-sulfur coal to prepare anode materials, thereby achieving higher sodium storage capacity and first coulombic efficiency, and improving the electrochemical performance of the battery. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a SEM image of bituminous coal from Embodiment 1 of the present invention.

[0029] Figure 2 These are SEM images of the dried and deashed coal powder from Embodiment 1 of the present invention.

[0030] Figure 3 These are SEM images of the anode material prepared from high-sulfur coal in Example 1 of this invention.

[0031] Figure 4 These are the electrochemical test curves of the high-sulfur coal anode materials of Examples 1, 1, 2, and 3 of this invention. Detailed Implementation

[0032] To facilitate understanding of the present invention, a more comprehensive description of the present invention will be given below, and embodiments of the present invention will be provided, but this does not limit the scope of the present invention.

[0033] In a first aspect, the present invention provides a method for preparing anode materials from high-sulfur coal, the specific steps of which include:

[0034] S1: Prepare a composite deashing solution by adding hydrochloric acid and nitric acid to deionized water;

[0035] S2: After crushing the high-sulfur coal, add it to the composite deashing solution described in S1 and stir to obtain a mixed solution;

[0036] S3: Dilute the mixed solution described in S2 with deionized water and filter it to obtain a filter cake. Dry the filter cake to obtain coal powder.

[0037] S4; The coal powder described in S3 is subjected to pre-carbonization treatment and high-temperature carbonization to obtain anode material prepared from high-sulfur coal;

[0038] Steps S1-S4 satisfy 0.01 ≤ 1.75 - 0.65c - 1.02α + 0.08c 2 +0.46α 2 +5.43e -0.735t ≤1, where 0.5≤α≤2; 2≤c≤6mol / L; t>0; α is the NO3 in the composite deashing solution described in S1. - Cl - The molar ratio, c is the H in the composite deashing solution described in S1. + The molar concentration of the substance, t is the stirring time in S2.

[0039] In the material design scheme of the present invention, high-sulfur coal is treated with the composite deashing solution system of the present invention, which can effectively remove sulfur minerals from the coal. On the one hand, the present invention uses hydrochloric acid and nitric acid to prepare the composite deashing solution, which can achieve the optimal etching degree of high-sulfur coal material, ensure the structural stability of high-sulfur coal material, and fully expose the inorganic minerals in high-sulfur coal, so as to better utilize NO3. - The dissolution effect of Cl - The strong coordination ability with metal impurity ions avoids excessive defects that cause impurity ion complexation and difficulty in removal. Furthermore, this invention regulates the balance of the two acids; when the balance meets the aforementioned formula range, it can effectively etch high-sulfur coal materials, thereby effectively removing encapsulated inorganic impurities. This allows for the selection of high-sulfur coal materials with suitable low ash content and high purity, resulting in higher sodium storage sites and improved sodium storage capacity of the anode material prepared from high-sulfur coal, leading to better electrochemical performance. Simultaneously, when using the composite deashing solution, appropriate time matching is required to achieve effective etching, ensuring sufficient reaction between the composite deashing solution and the high-sulfur coal to achieve optimal desulfurization.

[0040] To ensure that the high-sulfur coal material can be better adapted to the formula range while achieving etching, we need to adjust the ratio α of the composite deashing solution (specifically, the ratio of NO3 in the composite deashing solution). - Cl - (molar ratio), H in the composite deashing solution +The molar concentration c and the treatment conditions t (specifically, the stirring time of high-sulfur coal in the composite deashing solution) were regulated and optimized. α, c, and t have a synergistic correlation. When the regulated α, c, and t satisfy the above relationship, effective etching of the high-sulfur coal material can be achieved, better balancing the adsorption degree of acid radical ions and sulfur impurities in the composite deashing solution, avoiding excessive etching defects that affect the effective removal of inorganic impurities, screening out high-sulfur coal materials with suitable low ash content and high purity, enabling the high-sulfur coal material to obtain higher sodium storage sites, improving the sodium storage capacity of the negative electrode material prepared from high-sulfur coal, and obtaining better electrochemical performance.

[0041] Meanwhile, this invention considers that when the ratio and concentration of α and c are not coordinated, it will lead to excessive corrosion of coal-based materials and excessive adsorption and complexation with impurity metal ions, making it difficult for impurity metal ions to be removed by water washing and filtration. It may also lead to the ratio and concentration being too low to provide a sufficient acidic environment for etching, resulting in mineral residues, all of which are not conducive to improving the sodium storage capacity of high-sulfur coal anode materials. At this time, the cumulative change of time t is no longer able to obtain the synergistic regulation effect of α and c, exceeding the applicable range of the above formula. Therefore, in order to ensure that high-sulfur coal materials can be successfully etched in the composite deashing solution, this invention limits the range of α and c.

[0042] When α satisfies the above range (0.5≤α≤2) and c satisfies the above range (2≤c≤6mol / L), the composite deashing solution can be guaranteed to have sufficient acidity, NO3. - With Cl - A suitable molar ratio effectively promotes the dissolution and removal of sulfur minerals while avoiding excessive corrosion of high-sulfur coal materials; when α is too large, the NO3 in the composite deashing solution... - The concentration is relatively high, Cl - At relatively low concentrations, nitric acid tends to exhibit strong oxidizing properties, which may lead to excessive corrosion of coal-based materials, affecting their structural stability and causing excessive defects. It is also prone to adsorption and complexation with metal ions, making it difficult to remove through water washing and filtration. Lower Cl concentrations... - The concentration is insufficient to provide adequate coordination capacity, making it difficult to remove impurity metal ions. Conversely, when α is too small, Cl in the composite deashing solution... - The concentration of NO3 is relatively high. -While a relatively low concentration can provide strong coordination ability, it may not offer a sufficiently acidic environment for effective etching, leading to incomplete removal of sulfur minerals and ineffective etching. This results in high ash content in high-sulfur coal materials, which can clog sodium ion transport channels, negatively impacting the coulombic efficiency and capacity of the battery. Conversely, excessively high concentrations of C can cause over-corrosion of high-sulfur coal materials, while insufficient concentrations fail to provide a adequate acidic environment for effective etching. Furthermore, NO3- concentrations can also contribute to the problem. - With Cl - If the content is too low, the sulfur minerals cannot be fully dissolved, and the metal impurity ions cannot be removed. Therefore, when α and c exceed the above range, the synergistic correlation in the above formula range cannot be established. This invention ensures that the above formula can reflect the synergistic influence of α, c and t in the etching reaction of high-sulfur coal materials by reasonably controlling the range of α and c. Within the formula range, the problems of excessive corrosion and mineral residue are avoided at the same time, which is conducive to the increase of sodium storage sites and the improvement of sodium storage capacity of high-sulfur coal anode materials.

[0043] To ensure that the high-sulfur coal material reacts fully in the composite deashing solution, we can also adjust the time t according to the formula range to achieve the best desulfurization effect.

[0044] As a further embodiment, the S1 composite deashing solution contains: 0.6 ≤ α ≤ 1.3; 2.5 ≤ c ≤ 3.5 mol / L; 0.01 ≤ 1.75 - 0.65c - 1.02α + 0.08c 2 +0.46α 2 +5.43e -0.735t ≤0.2. When this formula meets this limitation, high-sulfur coal materials with suitable low ash content and high purity can be obtained, further increasing the sodium ion storage sites, increasing the sodium storage capacity of high-sulfur coal anode materials, and further improving electrochemical performance. Furthermore, the α and c values ​​selected within this formula range are beneficial to NO3. - With Cl - The molar ratio and concentration are effectively balanced to fully initiate the reaction and avoid excessive etching of high-sulfur coal by the composite deashing solution, thus ensuring the structural stability of the high-sulfur coal and fully exposing the inorganic minerals in the high-sulfur coal, thereby better utilizing NO3. - The dissolution effect of Cl - It has a strong coordination ability with metal impurity ions, avoiding the problem of excessive defects causing impurity ions to complex and become difficult to remove.

[0045] As a further embodiment, the pH value of the filtrate obtained by diluting and filtering with deionized water in S3 is 6-7. When the pH value of the filtrate obtained by diluting and filtering with deionized water is 6-7, the filtrate is neutral, which can ensure the effective removal of the composite deashing solution and inorganic components treated with the composite deashing solution from the coal powder. Improving the purity of the coal powder is beneficial to obtaining more sodium storage sites and increasing the sodium storage capacity of the negative electrode material prepared from high-sulfur coal.

[0046] As a further option, the pre-carbonization temperature in S4 is selected from 600≤T≤800℃, and the heating rate is 0.1-10℃ / min.

[0047] As a further option, the high-temperature carbonization temperature in S4 is selected from 1100≤T≤1500℃, and the heating rate is 0.1-10℃ / min.

[0048] Appropriate carbonization temperature and heating rate ensure the formation of a stable carbon structure in high-sulfur coal materials during carbonization, while avoiding sintering and structural damage caused by excessively high temperatures or heating rates. A suitable pre-carbonization temperature between 600 and 800 degrees Celsius effectively removes volatiles from high-sulfur coal after treatment with the composite deashing solution, while retaining some carbon structure, providing a good foundation for subsequent high-temperature carbonization. During the high-temperature carbonization stage, increasing the temperature to 1100 to 1500 degrees Celsius further enhances the carbonization degree of high-sulfur coal materials, forming a more stable graphitized carbon structure. This improves the conductivity of the material and increases the number of sodium storage sites, thereby increasing the sodium storage capacity of the anode material prepared from high-sulfur coal. Similarly, controlling the appropriate heating rate (0.1-10℃ / min) ensures uniform heating during carbonization, preventing cracks or structural damage caused by excessive temperature gradients that could affect the electrochemical performance of the material.

[0049] As a further option, the high-sulfur coal in S1 includes one or more of bituminous coal, anthracite, and coking coal.

[0050] As a further option, the drying device in S3 is one or more of the following: a blower dryer, a freeze dryer, a vacuum drying oven, a rotary flash dryer, and a hot air circulating drying oven.

[0051] Secondly, the present invention provides a negative electrode material prepared from high-sulfur coal, wherein the negative electrode material is obtained by the preparation method described in the first aspect.

[0052] Thirdly, this invention provides a sodium-ion battery negative electrode sheet prepared from high-sulfur coal. The negative electrode sheet comprises the sodium-ion battery negative electrode material prepared from high-sulfur coal as described in the second aspect of this invention, a conductive agent, and a binder. The high-sulfur coal-based negative electrode sheet provided by this invention possesses excellent sodium storage capacity and more sodium storage sites, enabling the battery to achieve higher capacity and longer cycle life during charge and discharge, exhibiting superior electrochemical performance in sodium-ion batteries.

[0053] This invention does not impose any particular limitation on the type of conductive agent, as long as it enhances the conductivity of the negative electrode and does not adversely affect the performance of the sodium-ion battery negative electrode material prepared from high-sulfur coal. Those skilled in the art can select conductive agents commonly used in the field according to actual needs. As some specific examples, the conductive agent used to prepare the negative electrode sheet can be selected from carbon blacks such as acetylene black and conductive carbon black, conductive polymers such as carbon nanotubes, graphene, graphite, polyaniline, and polythiophene, metal oxide conductive agents such as tin oxide and zinc oxide, and carbon nanofiber conductive agents, etc.

[0054] This invention does not impose any particular limitation on the type of binder, as long as it enhances the adhesion between the particles of the negative electrode active material and does not adversely affect the performance of the sodium-ion battery negative electrode material prepared from high-sulfur coal. Those skilled in the art can select the appropriate binder according to actual needs. As some specific examples, binders used to prepare the negative electrode sheet include polyvinylidene fluoride, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, polyimide, polystyrene sulfonic acid, polyacrylonitrile, polycarbonate, or polyetherimide ketone, etc.

[0055] Fourthly, this invention provides a sodium-ion battery, comprising the negative electrode, positive electrode, separator, and electrolyte described in the third aspect. The sodium-ion battery provided by this invention utilizes a negative electrode material prepared from high-sulfur coal, which not only possesses high energy density but also exhibits good stability during cycling, meeting the high capacity and long lifespan requirements of various electronic devices; it is widely used in portable electronic devices, electric vehicles, energy storage systems, and other applications requiring long-term operation and frequent charge-discharge cycles.

[0056] As a specific example of the implementation of this invention, detailed cases are provided below:

[0057] Example 1

[0058] (1) Place the bituminous coal in a pulverizing device and pulverize it to D. V50 =25um. Figure 1 (SEM image of bituminous coal)

[0059] (2) NO3 - Cl -Concentrated hydrochloric acid and concentrated nitric acid with a molar ratio of 0.825 were added to deionized water to prepare a 140 mL composite deashing solution with a hydrogen ion concentration of 3.1 mol / L.

[0060] (3) Take 35g of D V50 Bituminous coal with a density of 25 μm was added to the composite deashing solution, heated, and stirred. After 6 hours, deionized water was added for dilution. The diluted mixture was then filtered, and the filter cake was continuously rinsed with deionized water until the pH of the filtrate reached 6–7.

[0061] (4) Place the filter cake in a blower dryer to obtain dried coal powder. Figure 2 (SEM image of dried and deashed coal powder)

[0062] (5) Place 30g of dry coal powder in a tubular furnace and heat it to 700°C at a heating rate of 5°C / min. After holding it at that temperature for 3 hours, let it cool naturally to room temperature. After grinding, pre-carbonized deashed bituminous coal is obtained.

[0063] (6) Weigh 15g of pre-carbonized deashed bituminous coal, heat it to 1300℃ at a heating rate of 5℃ / min, keep it at that temperature for 3 hours, and then let it cool naturally to room temperature. After grinding, the negative electrode material prepared from high-sulfur coal is obtained. Figure 3 SEM image of anode material prepared from high-sulfur coal.

[0064] Example 2

[0065] NO3 - Cl - Concentrated hydrochloric acid and concentrated nitric acid in a molar ratio of 1.250 were added to deionized water to prepare a 140 mL composite deashing solution with a hydrogen ion concentration of 2.8 mol / L. The remaining steps and proportions were the same as in Example 1.

[0066] Example 3

[0067] NO3 - Cl - Concentrated hydrochloric acid and concentrated nitric acid in a molar ratio of 0.725 were added to deionized water to prepare a 140 mL composite deashing solution with a hydrogen ion concentration of 2.8 mol / L. The remaining steps were the same as in Example 1.

[0068] Example 4

[0069] (2) NO3 - Concentrated hydrochloric acid and concentrated nitric acid with a Cl- molar ratio of 1.52 were added to deionized water to prepare a 140 mL composite deashing solution with a hydrogen ion concentration of 2.1 mol / L.

[0070] (3) Take 35g of D V50Bituminous coal with a density of 25 μm was added to the composite deashing solution, heated, and stirred. After 7 hours, deionized water was added for dilution. The diluted mixture was then filtered, with deionized water continuously added to wash the filter cake until the pH of the filtrate reached 6-7. The remaining steps and proportions were the same as in Example 1.

[0071] Example 5

[0072] (2) NO3 - Cl - Concentrated hydrochloric acid and concentrated nitric acid with a molar ratio of 0.95 were added to deionized water to prepare a 140 mL composite deashing solution with a hydrogen ion concentration of 4.2 mol / L.

[0073] (3) Take 35g of D V50 Bituminous coal with a density of 25 μm was added to the composite deashing solution, heated, and stirred. After 4 hours, deionized water was added for dilution. The diluted mixture was then filtered, with deionized water continuously added to wash the filter cake until the pH of the filtrate reached 6-7. The remaining steps and proportions were the same as in Example 1.

[0074] Example 6

[0075] (2) NO3 - Cl - Concentrated hydrochloric acid and concentrated nitric acid in a molar ratio of 1.35 were added to deionized water to prepare a 140 mL composite deashing solution with a hydrogen ion concentration of 5.6 mol / L.

[0076] (3) Take 35g of D V50 Bituminous coal with a density of 25 μm was added to the composite deashing solution, heated, and stirred. After 3 hours, deionized water was added for dilution. The diluted mixture was then filtered, with deionized water continuously added to wash the filter cake until the pH of the filtrate reached 6-7. The remaining steps and proportions were the same as in Example 1.

[0077] Example 7

[0078] (2) NO3 - Concentrated hydrochloric acid and concentrated nitric acid with a Cl- molar ratio of 1.65 were added to deionized water to prepare a 140 mL composite deashing solution with a hydrogen ion concentration of 3.6 mol / L.

[0079] (3) Take 35g of D V50 Bituminous coal with a density of 25 μm was added to the composite deashing solution, heated, and stirred. After 5 hours, deionized water was added for dilution. The diluted mixture was then filtered, with deionized water continuously added to wash the filter cake until the pH of the filtrate reached 6-7. The remaining steps and proportions were the same as in Example 1.

[0080] Example 8

[0081] (2) NO3 - Concentrated hydrochloric acid and concentrated nitric acid with a Cl- molar ratio of 1.95 were added to deionized water, along with 140 mL of a 2.4 mol / L composite deashing solution. The remaining steps and proportions were the same as in Example 1.

[0082] (3) Take 35g of D V50 Bituminous coal with a density of 25 μm was added to the composite deashing solution, heated, and stirred. After 6 hours, deionized water was added for dilution. The diluted mixture was then filtered, with deionized water continuously added to wash the filter cake until the pH of the filtrate reached 6-7. The remaining steps and proportions were the same as in Example 1.

[0083] Example 9

[0084] (2) NO3 - Concentrated hydrochloric acid and concentrated nitric acid with a Cl- molar ratio of 0.525 were added to deionized water, along with 140 mL of a 5.8 mol / L composite deashing solution. The remaining steps and proportions were the same as in Example 1.

[0085] (3) Take 35g of D V50 Bituminous coal with a density of 25 μm was added to the composite deashing solution, heated, and stirred. After 3 hours, deionized water was added for dilution. The diluted mixture was then filtered, with deionized water continuously added to wash the filter cake until the pH of the filtrate reached 6-7. The remaining steps and proportions were the same as in Example 1.

[0086] Example 10

[0087] The deashing time was 4 hours, and the remaining steps were the same as in Example 2.

[0088] Example 11

[0089] The deashing time was 5 hours, and the remaining steps were the same as in Example 2.

[0090] Example 12

[0091] The deashing time was 7 hours, and the remaining steps were the same as in Example 2.

[0092] Comparative Example 1

[0093] (1) Take 30g of D V50 Bituminous coal with a density of 25 μm was placed in a tubular furnace and heated to 700°C at a heating rate of 5°C / min. After holding at this temperature for 3 hours, it was naturally cooled to room temperature and then ground to obtain pre-carbonized bituminous coal.

[0094] (2) Weigh 15g of pre-carbonized bituminous coal, heat it to 1300℃ at a heating rate of 5℃ / min, keep it at the temperature for 3 hours, and then cool it to room temperature naturally. After grinding, the negative electrode material prepared from high-sulfur coal is obtained.

[0095] Comparative Example 2

[0096] (1) Place the bituminous coal in a pulverizing device and pulverize it to D. V50 =25um.

[0097] (2) Prepare a 3.1 mol / L HNO3 solution using 68% concentrated nitric acid. Add 35 g of bituminous coal to 140 mL of the prepared HNO3 solution, heat and stir. After 6 h, dilute with deionized water. Then filter the diluted mixture by suction, continuously adding deionized water to rinse the filter cake until the pH of the filtrate reaches 6-7.

[0098] (3) The remaining steps are the same as in Example 1.

[0099] Comparative Example 3

[0100] (1) Prepare a 3.1 mol / L HCl solution by dissolving 37% concentrated hydrochloric acid. Add 35 g of bituminous coal to 140 mL of the prepared HCl solution, heat and stir. After 6 h, dilute with deionized water. Then filter the diluted mixture by suction, and continuously add deionized water to wash the filter cake until the pH of the filtrate reaches 6-7.

[0101] (7) The remaining steps are the same as in Example 1.

[0102] Comparative Example 4

[0103] The deashing time is 1 hour, and the remaining steps are the same as in Example 2.

[0104] Comparative Example 5

[0105] The deashing time was 10 hours, and the remaining steps were the same as in Example 2.

[0106] Comparative Example 6

[0107] (2) NO3 - Concentrated hydrochloric acid and concentrated nitric acid with a Cl- molar ratio of 0.2 were added to deionized water, along with 140 mL of a 1.5 mol / L composite deashing solution. The remaining steps and proportions were the same as in Example 1.

[0108] (3) Take 35g of D V50 Bituminous coal with a density of 25 μm was added to the composite deashing solution, heated, and stirred. After 8 hours, deionized water was added for dilution. The diluted mixture was then filtered, with deionized water continuously added to wash the filter cake until the pH of the filtrate reached 6-7. The remaining steps and proportions were the same as in Example 1.

[0109] Comparative Example 7

[0110] (2) NO3 -Cl - Concentrated hydrochloric acid and concentrated nitric acid in a molar ratio of 3.5 were added to deionized water, along with 140 mL of a 6.5 mol / L composite deashing solution. The remaining steps and proportions were the same as in Example 1.

[0111] (3) Take 35g of D V50 Bituminous coal with a density of 25 μm was added to the composite deashing solution, heated, and stirred. After 4 hours, deionized water was added for dilution. The diluted mixture was then filtered, with deionized water continuously added to wash the filter cake until the pH of the filtrate reached 6-7. The remaining steps and proportions were the same as in Example 1.

[0112] Comparative Example 8

[0113] (2) NO3 - Cl - Concentrated hydrochloric acid and concentrated nitric acid in a molar ratio of 2.5 were added to deionized water, along with 140 mL of a 0.3 mol / L composite deashing solution. The remaining steps and proportions were the same as in Example 1.

[0114] (3) Take 35g of D V50 Bituminous coal with a density of 25 μm was added to the composite deashing solution, heated, and stirred. After 8 hours, deionized water was added for dilution. The diluted mixture was then filtered, with deionized water continuously added to wash the filter cake until the pH of the filtrate reached 6-7. The remaining steps and proportions were the same as in Example 1.

[0115] Comparative Example 9

[0116] (2) NO3 - Cl - Concentrated hydrochloric acid and concentrated nitric acid with a molar ratio of 0.2 were added to deionized water, along with 140 mL of a 7.5 mol / L composite deashing solution. The remaining steps and proportions were the same as in Example 1.

[0117] (3) Take 35g of D V50 Bituminous coal with a density of 25 μm was added to the composite deashing solution, heated, and stirred. After 3 hours, deionized water was added for dilution. The diluted mixture was then filtered, with deionized water continuously added to wash the filter cake until the pH of the filtrate reached 6-7. The remaining steps and proportions were the same as in Example 1.

[0118] Specific testing conditions and methods:

[0119] The process of preparing the electrode sheet using the following materials: 450 mg of negative electrode material powder prepared from high-sulfur coal was used as the active material and mixed evenly with conductive carbon (SuperP) and binder (PVDF) at a mass ratio of 90:5:5. The mixture was then transferred to the feed tank of a degassing machine (MAZERUSTAR degassing machine). 650 μL of N-methylpyrrolidone (NMP) solvent was added for further mixing, homogenization, and defoaming. The instrument was run on the Ratation 9 program for 10 minutes. The prepared slurry was then coated onto an aluminum foil current collector and placed in a vacuum drying oven at 120℃ for 6 hours until the material was completely dry. The aluminum foil was then removed and cut into round sheets with a diameter of 12 mm.

[0120] Electrochemical performance testing methods:

[0121] 0.1C constant current discharge to 0V (sodium intercalation);

[0122] Let stand for 10 minutes

[0123] 0.02C constant current discharge to 0V

[0124] Let stand for 10 minutes

[0125] Charge at a constant current of 0.1C to 2V (sodium removal);

[0126] Let stand for 10 minutes

[0127] Table 1

[0128]

[0129]

[0130]

[0131] As can be seen from the data in Table 1, Examples 1-12 and Comparative Examples 1-9 exhibit higher charging capacity and first-cycle coulombic efficiency, while also having relatively low ash content. The numerical values ​​reflected by the formula show a small error compared to the actual measured ash content. This indicates that by controlling the balance between the two acids in the composite deashing solution, the formula 0.01 ≤ 1.67 - 0.65c - 1.02α + 0.08c can be achieved. 2 +0.46α 2 +5.43e -0.735t When the ash content is ≤1, high-sulfur coal anode materials with relatively low ash content can be successfully prepared and screened, thereby obtaining more sodium storage sites, widening the sodium ion transport channels, and effectively improving the sodium storage capacity and coulombic efficiency of the battery.

[0132] Figure 1 The image shows an SEM image of bituminous coal, which reveals fine particles on the surface of the coal material. Figure 2 SEM images of dried and deashed coal powder, by Figure 1 and Figure 2 The comparison shows that the material surface becomes smoother after composite deashing, indicating that the mineral impurities in the coal are effectively removed. Figure 3 SEM images of the anode material prepared from high-sulfur coal show that the conductivity of the material is improved after high-temperature carbonization.

[0133] Based on the comparison of Example 1 and Comparative Examples 1-3, and the data in Table 1, it can be seen that compared to the ash content of bituminous coal not treated with the composite deashing solution and bituminous coal deashed using either nitric acid or hydrochloric acid, the ash content of the deashed bituminous coal treated with the composite deashing solution of nitric acid and hydrochloric acid in Example 1 was reduced to 0.02%, and it exhibited higher battery capacity and first-cycle coulombic efficiency. This is because the composite deashing solution simultaneously contains NO3-. - and Cl - On the one hand, it can give full play to NO3 - Its strong oxidizing properties better etch the organic matter in coal, fully dissolving inorganic sulfur minerals and removing them from the coal's organic matter; on the other hand, it utilizes Cl... - Its strong coordination ability allows it to coordinate with metal ions in coal minerals, thereby removing these minerals. When a composite deashing solution is not used, etching of high-sulfur coal cannot be initiated, and its inorganic sulfur minerals cannot be effectively dissolved and removed. Furthermore, when only nitric acid or hydrochloric acid is used to treat high-sulfur coal, NO3 cannot be effectively balanced. - The strong oxidizing properties and Cl - The strong coordination ability of NO3 leads to the deashing solution tending to exhibit only NO3. - The strong oxidizing properties of the material cause excessive etching, resulting in large surface defects, or only revealing Cl. - Its strong coordination ability removes some metal impurity ions, but it cannot fully dissolve inorganic sulfur minerals, resulting in high ash content, which affects sodium storage capacity and coulombic efficiency.

[0134] Depend on Figure 4 It can be seen that among the electrochemical test curves of Example 1 and Comparative Examples 1-3, Example 1 has the highest reversible capacity, indicating that effective deashing can release more sodium storage sites occupied by inorganic minerals and improve the sodium storage capacity of high-sulfur coal anode materials.

[0135] When changing α and c, the corresponding time t needs to be adjusted to meet the formula range, thereby obtaining a relatively low ash content and improving electrochemical performance. As can be seen from Example 1 and Comparative Examples 6-9, when the ratio and concentration of α and c are not coordinated, it is not conducive to initiating the etching reaction, and the ash content and electrochemical performance are lower than in the examples. This indicates that NO3 needs to be controlled. - With Cl- The molar ratio and H in the composite deashing solution + The concentration of the substance is further controlled. The controlled composite deashing solution can provide an appropriate acid concentration to effectively etch high-sulfur coal materials, maintain structural integrity, and better balance the oxidizing and coordination capabilities of the composite deashing solution. This achieves optimized deashing treatment of high-sulfur coal materials, obtains higher desulfurization effect, improves sodium ion storage sites, broadens sodium ion transport channels, and has better battery sodium storage capacity and coulombic efficiency.

[0136] As can be seen from Examples 1-3 and Examples 4-10, when 0.01 ≤ 1.75 - 0.65c - 1.02α + 0.08c 2 +0.46α 2 +5.43e -0.735t When the ash content of high-sulfur coal anode materials is ≤0.2, 0.6≤α≤1.3, and 2.5≤c≤3.5mol / L, the ash content is relatively low, and the sodium storage capacity and coulombic efficiency of the battery are relatively high. This indicates that within this control range, the selected NO3... - With Cl - The molar ratio and H in the composite deashing solution + The molar concentration of NO3 can reach the optimal equilibrium ratio, giving full play to its properties. - Oxidizing properties and Cl - Its coordination ability allows it to better dissolve inorganic sulfur minerals and combine with and remove metal impurity ions under appropriate acidity, maintain a more complete high-sulfur coal material structure, obtain the best etching defects, minimize the impact of impurities, increase sodium ion storage sites, and improve its sodium storage performance.

[0137] As can be seen from Examples 2, 10-12, and Comparative Examples 4-5, when α and c are kept within a certain range, adjusting the time t will satisfy the preferred range of the formula (0.01≤1.75-0.65c-1.02α+0.08c). 2 +0.46α 2 +5.43e -0.735tWhen the ash content is ≤0.2%, a relatively low ash content and a high sodium storage capacity can be obtained. This indicates that t within the formula range can ensure that the high-sulfur coal material reacts fully in the composite deashing solution, achieving effective etching. Examples 2 and 4 and 5 show that when t is not within the formula range, the ash content of the high-sulfur coal material increases, and the electrochemical performance decreases, which is not conducive to the full and effective etching and desulfurization of the high-sulfur coal material. This indicates that by selecting α and c within the range defined by the above formula, an appropriate reaction time can be selected to ensure that the composite deashing solution fully contacts and reacts with the inorganic minerals of the high-sulfur coal, improving the purification efficiency of the high-sulfur coal, achieving the best desulfurization effect, improving the electrochemical performance of the battery, and avoiding the impact of improper time matching on the etching effect and the structural integrity of the high-sulfur coal material.

[0138] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing anode materials from high-sulfur coal, comprising the following steps: S1: Prepare a composite deashing solution by adding hydrochloric acid and nitric acid to deionized water; S2: After crushing the high-sulfur coal, add it to the composite deashing solution described in S1, and heat and stir to obtain a mixed solution; S3: Dilute the mixed solution described in S2 with deionized water and filter it to obtain a filter cake. Dry the filter cake to obtain coal powder. S4; The coal powder described in S3 is subjected to pre-carbonization treatment and high-temperature carbonization to obtain anode material prepared from high-sulfur coal; Steps S1-S4 satisfy 0.01 ≤ 1.75 - 0.65c - 1.02α + 0.08c 2 +0.46α 2 +5.43e -0.735t ≤1, where 0.5≤α≤2; 2≤c≤6mol / L; t>0; α is the NO3 in the composite deashing solution described in S1. - Cl - The molar ratio, c is the H in the composite deashing solution described in S1. + The molar concentration of the substance, t is the stirring time in S2.

2. The method for preparing anode materials from high-sulfur coal according to claim 1, characterized in that, In the S1 composite deashing solution, 0.6 ≤ α ≤ 1.3; 2.5 ≤ c ≤ 3.5 mol / L; 0.01 ≤ 1.75 - 0.65c - 1.02α + 0.08c 2 +0.46α 2 +5.43e -0.735t ≤0.

2.

3. The method for preparing anode materials from high-sulfur coal according to claim 1, characterized in that, The pH value of the filtrate after dilution with deionized water and filtration in S3 is 6-7.

4. The method for preparing anode materials from high-sulfur coal according to claim 1, characterized in that, The pre-carbonization temperature in S4 is selected from 600≤T≤800℃, the high-temperature carbonization temperature is selected from 1100≤T≤1500℃, and the heating rate is 0.1-10℃ / min.

5. The method for preparing anode materials from high-sulfur coal according to claim 1, characterized in that, The high-sulfur coal in S1 includes one or more of bituminous coal, anthracite, and coking coal.

6. As a further embodiment, the drying device in S3 is one or more of the following: a blower dryer, a freeze dryer, a vacuum drying oven, a rotary flash dryer, and a hot air circulating drying oven.

7. A negative electrode material prepared from high-sulfur coal, characterized in that, The negative electrode material is obtained by the preparation method according to any one of claims 1-6.

8. A sodium-ion battery negative electrode sheet prepared from high-sulfur coal, characterized in that, The sodium-ion battery anode sheet prepared from high-sulfur coal is made of the sodium-ion battery anode material prepared from high-sulfur coal as described in claim 7, a conductive agent, and a binder.

9. A sodium-ion battery, characterized in that, The sodium-ion battery includes the negative electrode, positive electrode, separator, and electrolyte as described in claim 8.

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