Pre-sodium hard carbon material as well as preparation method and application thereof
By optimizing the molecular and pore structures of hard carbon materials through the pre-sodiumization reaction of doped carbon sources and organic sodium salts, the problems of low initial coulombic efficiency and poor cycle performance of hard carbon materials in sodium-ion batteries are solved, thus achieving a high-efficiency improvement in sodium-ion battery performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-14
- Publication Date
- 2026-04-21
AI Technical Summary
When existing hard carbon materials are used as anode materials for sodium-ion batteries, they suffer from low initial coulombic efficiency, poor cycle performance, and low energy density. Furthermore, existing pre-sodiumification methods are either highly dangerous or complex to operate.
By mixing carbon source, amino acids and phosphoric acid for pre-carbonization reaction to form doped carbon source, and then carrying out pre-sodiumization reaction with organic sodium salt in a weakly alkaline environment, pre-sodiumized hard carbon material is finally prepared through carbonization reaction. Nitrogen and phosphorus elements are introduced to form closed-pore structure, optimize molecular structure and pore structure, and improve sodium ion intercalation performance.
The prepared pre-sodium hard carbon material significantly improves the first coulombic efficiency, cycle performance, and battery capacity of sodium-ion batteries. It is simple to operate and highly safe, making it suitable for commercial production.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of electrochemical materials technology, specifically to a pre-sodium-modified hard carbon material, its preparation method, and its application. Background Technology
[0002] In recent years, sodium-ion batteries have experienced rapid development and practical application due to the abundant, widely distributed, and low-cost nature of sodium resources. They are expected to become a substitute for lithium-ion batteries, possessing broad application and commercial prospects. However, their low energy density and poor cycle stability have become technical bottlenecks restricting further development. Therefore, developing a low-cost and high-performance anode material suitable for sodium-ion batteries is currently a key strategy.
[0003] Currently, hard carbon is considered the most suitable anode material for sodium-ion batteries. Due to the large radius of sodium ions, and the large interlayer spacing and well-developed pore structure of hard carbon, it possesses superior sodium storage capacity compared to traditional anode materials such as graphite. Combined with its low cost and suitable redox potential for sodium, hard carbon is considered the most valuable anode material for sodium-ion batteries for research investment. However, the abundant porosity and active defect sites in hard carbon can lead to continuous electrolyte decomposition and the formation of a solid electrolyte interphase (SEI), resulting in a decrease in the initial coulombic efficiency of the hard carbon anode. A large amount of irreversible sodium ions are consumed, and all irreversible sodium ions in the entire battery system are entirely provided by the cathode material. Since the amount of cathode material is limited, the remaining sodium ions are insufficient to guarantee subsequent cycles, leading to poor cycle performance and low energy density.
[0004] To improve the initial coulombic efficiency of hard carbon anodes, a pre-sodiumization method can be used. Pre-sodiumization is a technical treatment process for hard carbon anode materials in sodium-ion batteries, aiming to introduce a certain amount of sodium ions into the hard carbon anode material before the battery's first charge and discharge. However, current pre-sodiumization methods either involve the use of metallic sodium, which is highly dangerous; or the operation process and equipment are complex, hindering production; or the resulting pre-sodiumized hard carbon materials do not perform well enough, offering limited performance improvement for sodium-ion batteries. Therefore, developing a pre-sodiumization method for hard carbon materials that is simple to operate, safe, and has better performance is crucial. Summary of the Invention
[0005] The purpose of this invention is to overcome the problems existing in the prior art and to provide a pre-sodium-modified hard carbon material, its preparation method, and its application.
[0006] To achieve the above objectives, the present invention provides a method for pre-sodiumizing hard carbon materials, the method comprising:
[0007] (1) A carbon source, amino acids and phosphoric acid are mixed and pre-carbonized to obtain a doped carbon source;
[0008] (2) Provide a dispersion containing the doped carbon source, surfactant and weak base, and introduce an organic sodium salt to carry out a pre-sodiumization reaction to obtain a hard carbon precursor;
[0009] (3) The hard carbon precursor is subjected to a carbonization reaction to obtain a pre-sodiumized hard carbon material;
[0010] The weight ratio of the carbon source to the amino acid is 1:0.4-1.4, and the temperature of the pre-carbonization reaction is 300-800℃.
[0011] A second aspect of the present invention provides a pre-sodium-modified hard carbon material, which is prepared by the pre-sodium modification method described above for hard carbon materials.
[0012] A third aspect of the present invention provides a negative electrode comprising the aforementioned pre-sodium-modified hard carbon material.
[0013] A fourth aspect of the present invention provides a sodium-ion battery comprising the aforementioned pre-sodium-modified hard carbon material or a negative electrode.
[0014] This invention introduces nitrogen and phosphorus elements into a carbon source through a pre-carbonization reaction to obtain a doped carbon source. The doped carbon source possesses numerous active sites and abundant closed-pore structures, enhancing sodium storage capacity and providing favorable conditions for the introduction of sodium ions in the subsequent pre-sodiumization reaction. The pre-sodiumization reaction introduces sodium ions through coordination complexation and cross-linking reactions between the doped carbon source and organic sodium salts, optimizing the molecular and pore structures and supplementing the carbon content. Finally, the thermoelectric field provided by the carbonization reaction drives the intercalation of sodium ions, resulting in a high-performance pre-sodiumized hard carbon material. The pre-sodiumization method of this invention is simple to operate, highly safe, and requires no complex equipment or metallic sodium. The raw materials used are inexpensive and abundant, facilitating commercial-scale production. The obtained pre-sodiumized hard carbon material exhibits excellent performance, significantly improving the initial coulombic efficiency, cycle performance, and battery capacity of sodium-ion batteries. Detailed Implementation
[0015] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0016] This invention provides a method for pre-sodiuming hard carbon materials, the method comprising:
[0017] (1) A carbon source, amino acids and phosphoric acid are mixed and pre-carbonized to obtain a doped carbon source;
[0018] (2) Provide a dispersion containing the doped carbon source, surfactant and weak base, and introduce an organic sodium salt to carry out a pre-sodiumization reaction to obtain a hard carbon precursor;
[0019] (3) The hard carbon precursor is subjected to a carbonization reaction to obtain a pre-sodiumized hard carbon material;
[0020] The weight ratio of the carbon source to the amino acid is 1:0.4-1.4, and the temperature of the pre-carbonization reaction is 300-800℃.
[0021] According to the present invention, in the pre-carbonization reaction, doping the carbon source and controlling the content of the doping elements within a reasonable range can significantly improve the electrochemical performance of hard carbon materials and enhance their electron mobility. Simultaneously, doping with nitrogen and phosphorus elements enables the doped carbon source to possess a richer closed-pore structure, which can increase sodium storage sites.
[0022] According to the present invention, in order to achieve a larger sodium storage capacity to facilitate the introduction of sodium ions in the subsequent pre-sodiumization reaction, thereby maximizing the performance of hard carbon materials, preferably, the weight ratio of the carbon source and amino acids is 1:0.4-1, for example, it can be 1:0.4, 1:0.6, 1:0.7 and 1:1 and any range between these values.
[0023] According to the present invention, in order to increase the closed-pore structure of the doped carbon source to provide more sodium storage sites and enhance the electrochemical activity of the hard carbon material, preferably, the weight ratio of the carbon source to phosphoric acid is 1:0.1-0.3, more preferably 1:0.1-0.2, for example, it can be 1:0.1, 1:0.14, 1:0.17 and 1:0.2 and any range between these values. The amount of phosphoric acid used refers to the weight of the phosphoric acid itself, excluding the weight of water. For example, when using 10g of a 50wt% phosphoric acid aqueous solution, the actual amount of phosphoric acid used is 5g.
[0024] According to the present invention, the doped carbon source is formed through a pre-carbonization reaction of the carbon source, amino acids, and phosphoric acid. Then, pre-sodiumization and carbonization are performed using raw materials containing the doped carbon source to obtain a pre-sodiumized hard carbon material with a high sodium content. This pre-sodiumized hard carbon material can significantly improve the plateau capacity, initial coulombic efficiency, and cycle stability of sodium-ion batteries. To ensure better coordination of the carbon source, amino acids, and phosphoric acid to obtain a pre-sodiumized hard carbon material with better performance, preferably, the carbon source is selected from one or more of starch, maltodextrin, phenolic resin, epoxy resin, cellulose, glucose, sucrose, maltose, lactose, and fructose, and more preferably from one or more of starch, maltodextrin, phenolic resin, and glucose. Preferably, the amino acid is selected from one or more of alanine, lysine, aspartic acid, glycine, serine, and tryptophan, and more preferably from one or more of alanine, lysine, and aspartic acid. Preferably, the phosphoric acid can be provided in solution form, preferably a 30-50 wt% aqueous solution of phosphoric acid, and more preferably a 40-50 wt% aqueous solution of phosphoric acid.
[0025] According to the present invention, the carbon source, amino acids, and phosphoric acid are mixed before the pre-carbonization reaction to ensure good contact between the components. To achieve more thorough mixing and uniform distribution of the components, thereby obtaining a higher quality doped carbon source, the mixing time is preferably 0.1-2 hours, more preferably 0.5-1 hour, and can be, for example, 0.5 hours, 0.6 hours, 0.9 hours, and 1 hour, or any range thereof. The mixing temperature is preferably 10-50°C, more preferably 20-35°C, and can be, for example, 22°C, 25°C, 30°C, and 35°C, or any range thereof. The mixing stirring speed is preferably 50-300 r / min, more preferably 100-200 r / min, and can be, for example, 100 r / min, 130 r / min, 170 r / min, and 200 r / min, or any range thereof.
[0026] According to the present invention, the pre-carbonization reaction enables nitrogen and phosphorus elements to be fully doped into the pre-carbonized carbon source. During this pre-carbonization reaction, the formed doped carbon source can develop more closed-pore structures, thereby increasing sodium storage sites. To obtain a doped carbon source with a more suitable particle size, higher specific surface area, and better stability, facilitating the introduction of sodium ions in the subsequent pre-sodiumization reaction, preferably, the temperature of the pre-carbonization reaction is 300-600℃, for example, values such as 330℃, 460℃, 550℃, and 600℃, or any range thereof. Excessively high temperatures in the pre-carbonization reaction will reduce the specific surface area of the doped carbon source and decrease its performance; excessively low temperatures will make it difficult to achieve the pre-carbonization purpose, hindering elemental doping and reducing sodium storage sites. Preferably, the pre-carbonization reaction time is 2-8 hours, preferably 2-5 hours, for example, values such as 2 hours, 5 hours, 7 hours, and 7.5 hours, or any range thereof. Preferably, the pre-carbonization reaction is carried out under an inert atmosphere, the inert atmosphere being selected from one or more of nitrogen and argon.
[0027] According to the present invention, the pre-sodiumization reaction, while introducing sodium ions, also optimizes the molecular and pore structures through coordination complexation and cross-linking reactions between the doped carbon source and the organic sodium salt. To enhance the reactivity of the pre-sodiumization reaction and obtain a higher quality hard carbon precursor, preferably, the weight ratio of the doped carbon source to the surfactant is 1:0.05-0.25, more preferably 1:0.05-0.15, and for example, values such as 1:0.07, 1:0.1, 1:0.13, and 1:0.15, or any range thereof. Preferably, the weight ratio of the doped carbon source to the weak base is 1:0.5-2, more preferably 1:0.5-1, and for example, values such as 1:0.5, 1:0.7, 1:0.8, and 1:1, or any range thereof. Preferably, the weight ratio of the doped carbon source to the organic sodium salt is 1:0.2-0.8, more preferably 1:0.2-0.6, and can be, for example, 1:0.25, 1:0.3, 1:0.5, and 1:0.6, or any range thereof. Preferably, the temperature of the pre-sodiumization reaction is 15-60℃, more preferably 15-40℃, and can be, for example, 20℃, 25℃, 30℃, and 40℃, or any range thereof. Preferably, the time of the pre-sodiumization reaction is 6-12 hours, more preferably 6-8 hours, and can be, for example, 6 hours, 6.5 hours, 7 hours, and 8 hours, or any range thereof.
[0028] According to the present invention, the surfactant can enhance the reactivity of the pre-sodiumization reaction, promote the occurrence and progress of the reaction, and in order to further improve the reaction efficiency and obtain a better pre-sodiumization product, preferably, the surfactant is selected from one or more of hexadecyltrimethylammonium bromide, sodium fatty alcohol polyoxyethylene ether sulfate, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, polyoxyethylene fatty alcohol ether and polysorbate, preferably one or more of hexadecyltrimethylammonium bromide, sodium dodecylbenzene sulfonate and polysorbate.
[0029] According to the present invention, the pre-sodiumization reaction is carried out in a weakly alkaline environment. To provide a more suitable weakly alkaline environment and promote the reaction, preferably, the weak base is selected from one or more of potassium bicarbonate, sodium bicarbonate, ammonium bicarbonate, ammonia, and urea, and more preferably from one or more of ammonium bicarbonate and ammonia. When the weak base is ammonia, the amount of ammonia used is based on the weight of ammonia therein, and the concentration of the ammonia is 45-65 wt%, for example, 10g of 50 wt% ammonia, wherein the weight of ammonia is 5g.
[0030] According to the present invention, after the pre-sodiumization reaction, some carbon content is lost during the purification process. The reaction between the organic sodium salt and the doped carbon source not only optimizes the molecular structure and introduces sodium ions, but also replenishes some carbon content, ensuring the stability of the hard carbon content in subsequent carbonization reactions. To obtain a pre-sodiumized hard carbon material with better performance, preferably, the organic sodium salt is selected from one or more of sodium carboxymethyl cellulose, sodium alginate, sodium gluconate, monosodium glutamate, sodium phytate, sodium citrate, and sodium lactate, and more preferably from one or more of sodium alginate, sodium gluconate, sodium phytate, and sodium citrate.
[0031] According to the present invention, the dispersion containing the doped carbon source, surfactant, and weak base is obtained by dispersing the doped carbon source, surfactant, and weak base in a solvent by stirring. The stirring time can be selected within a wide range. To ensure that the doped carbon source, surfactant, and weak base are fully dispersed and uniformly distributed, facilitating the pre-sodiumization reaction, the stirring time is preferably 0.5-3 hours, more preferably 0.5-2 hours, for example, values such as 0.5 hours, 1 hour, 1.5 hours, and 2 hours, and any range between these values.
[0032] According to the present invention, the solvent and its amount in the dispersion can be selected within a wide range. To improve the efficiency of the pre-sodiumization reaction, preferably, the amount of solvent relative to 1g of the doped carbon source is 10-50mL, more preferably 15-30mL, for example, 17mL, 20mL, 24mL, and 28mL, or any value between these values. Preferably, the solvent of the dispersion is selected from a mixture of an organic solvent and water. Preferably, the volume ratio of the organic solvent to water is 1:2-6, more preferably 1:3-5, for example, 1:3, 1:4, 1:4.5, and 1:5, or any value between these values. Preferably, the organic solvent is selected from one or more of methanol, ethanol, tetrahydrofuran, acetone, and dioxane, more preferably methanol and / or ethanol.
[0033] According to the present invention, in order to obtain the hard carbon precursor with better quality, a post-processing can be performed after the pre-sodiumization reaction. The post-processing method can be selected from commonly used post-processing methods in the art. Preferably, the post-processing method is to centrifuge, wash and dry in sequence.
[0034] According to the present invention, the centrifugation conditions can be selected within a wide range. For better solid-liquid separation, preferably, the centrifugation speed is 5000-10000 r / min, more preferably 6000-8000 r / min, for example, it can be 6500 r / min, 7200 r / min, 7600 r / min, and 8000 r / min, or any value between these ranges. Preferably, the centrifugation time is 2-10 min, more preferably 4-8 min, for example, it can be 4 min, 5 min, 7 min, and 8 min, or any value between these ranges.
[0035] According to the present invention, the detergent and the number of washes can be selected within a wide range. In order to better remove residual reagents and impurities, the detergent can preferably be selected from one or more of deionized water, methanol, ethanol, tetrahydrofuran, acetone and dioxane, and more preferably one or more of deionized water, methanol and ethanol.
[0036] According to the present invention, the drying conditions can be selected within a wide range. To better remove residual moisture and organic solvents and obtain the dried hard carbon precursor, the drying temperature is preferably 60-100°C, more preferably 70-90°C, for example, values such as 70°C, 80°C, 85°C, and 90°C, and any range thereof. Preferably, the drying time is 8-20 hours, more preferably 10-15 hours, for example, values such as 10 hours, 12 hours, 14 hours, and 15 hours, and any range thereof.
[0037] According to the present invention, in the carbonization reaction, the rapid heating process provides the driving force of the thermal field, the applied voltage provides the driving force of the electric field, and the oxygen-containing functional groups and defect sites provide the chemical adsorption force. Under the driving force of these three forces, sodium ions will be pre-stored in the oxygen-containing functional groups and defect sites, ultimately obtaining the pre-sodium-modified hard carbon material. To enable the pre-sodium-modified hard carbon material to possess superior electrochemical and kinetic properties, preferably, the voltage of the carbonization reaction is 3.2-4V, more preferably 3.2-3.5V, for example, values such as 3.2V, 3.3V, 3.4V, and 3.5V, and any range thereof. Preferably, the pressure of the carbonization reaction is 20-30MPa, more preferably 22-25MPa, for example, values such as 22MPa, 23MPa, 24MPa, and 25MPa, and any range thereof. Preferably, the carbonization reaction temperature is 1100-1500℃, more preferably 1100-1300℃, for example, it can be 1100℃, 1200℃, 1250℃, and 1300℃, or any range thereof. Preferably, the carbonization reaction time is 5-12 min, more preferably 5-8 min, for example, 5 min, 6 min, 7 min, and 8 min, or any range thereof. Preferably, the carbonization reaction heating rate is 200-500℃ / min, more preferably 300-400℃ / min, for example, 300℃ / min, 330℃ / min, 380℃ / min, and 400℃ / min, or any range thereof. Preferably, the carbonization reaction is carried out in an inert atmosphere, the inert atmosphere being selected from one or more of nitrogen and argon.
[0038] A second aspect of the present invention provides a pre-sodium-modified hard carbon material, which is prepared by the pre-sodium modification method described above for hard carbon materials.
[0039] A third aspect of the present invention provides a negative electrode comprising the aforementioned pre-sodium-modified hard carbon material.
[0040] A fourth aspect of the present invention provides a sodium-ion battery comprising the aforementioned pre-sodium-modified hard carbon material or a negative electrode.
[0041] The pre-sodiumification method of this invention involves interconnected and mutually reinforcing steps. Step (1) grows abundant closed-pore structures while doping with nitrogen and phosphorus, thus providing more sodium storage sites for the introduction of sodium ions in step (2). Step (2) introduces sodium ions, optimizes the molecular structure, and supplements some carbon content, resulting in superior performance of the pre-sodiumified hard carbon material obtained in the subsequent carbonization reaction in step (3). The pre-sodiumification method of this invention is simple to operate, highly safe, and produces pre-sodiumified hard carbon materials with excellent performance, effectively solving the problems of low energy density and poor cycle performance in sodium-ion batteries.
[0042] The present invention will be described in detail below through embodiments.
[0043] The apparatus used in the following examples are all conventional experimental apparatuses in this field, and the raw materials and reagents used are all commercially available.
[0044] Example 1
[0045] (1) Mix 5g starch, 4g aspartic acid and 1.2g of 45wt% phosphoric acid aqueous solution at 25℃ with a stirring speed of 100r / min for 0.5h, and then pre-carbonize the mixture at 500℃ under an argon atmosphere for 3h. The pre-carbonized product is then pulverized to obtain a doped carbon source.
[0046] (2) 3g of doped carbon source, 0.3g of hexadecyltrimethylammonium bromide, and 3.6g of 50wt% ammonia were added to a mixed solvent of 12mL ethanol and 48mL water and stirred for 1h. Then, 1.5g of sodium citrate was added, and the reaction was pre-sodiumized at 30℃ for 6h. After the reaction was completed, the reaction solution was centrifuged at 6000r / min for 5min. The solid was taken out and washed three times with deionized water and ethanol respectively. After drying at 80℃ for 12h, it was pulverized to obtain the hard carbon precursor.
[0047] (3) The hard carbon precursor was placed in a plasma sintering furnace, and a voltage of 3.5V and a pressure of 22MPa were applied under an argon atmosphere. The temperature was increased to 1300℃ at a heating rate of 300℃ / min. After the carbonization reaction was carried out for 6 minutes, the temperature was naturally cooled to room temperature to obtain the pre-sodium hard carbon material.
[0048] Example 2
[0049] (1) Mix 5g of maltodextrin, 2g of alanine and 2.5g of 40wt% phosphoric acid aqueous solution at 20℃ with a stirring speed of 150r / min for 1h, and then pre-carbonize the mixture at 300℃ under an argon atmosphere for 5h. The pre-carbonized product is then pulverized to obtain a doped carbon source.
[0050] (2) 3g of doped carbon source, 0.45g of sodium dodecylbenzenesulfonate, and 4g of 60wt% ammonia were added to a mixed solvent of 15mL ethanol and 75mL water and stirred for 0.5h. Then, 1.8g of sodium alginate was added, and the mixture was pre-sodiumized at 20℃ for 8h. After the reaction was completed, the reaction solution was centrifuged at 8000r / min for 4min. The solid was taken out and washed three times with deionized water and ethanol, respectively. After drying at 90℃ for 15h, it was pulverized to obtain the hard carbon precursor.
[0051] (3) The hard carbon precursor was placed in a plasma sintering furnace, and a voltage of 3.2V and a pressure of 25MPa were applied under an argon atmosphere. The temperature was increased to 1200℃ at a heating rate of 400℃ / min. After carbonization reaction for 5 minutes, the material was naturally cooled to room temperature to obtain pre-sodium hard carbon material.
[0052] Example 3
[0053] (1) Mix 5g of maltodextrin, 4g of lysine and 1.5g of 50wt% phosphoric acid aqueous solution at 35℃ with a stirring speed of 200r / min for 1h, and then pre-carbonize the mixture at 600℃ under an argon atmosphere for 5h. The pre-carbonized product is then pulverized to obtain a doped carbon source.
[0054] (2) 3g of doped carbon source, 0.4g of hexadecyltrimethylammonium bromide and 1.8g of ammonium bicarbonate were added to a mixed solvent of 20mL ethanol and 60mL water and stirred for 2h. Then, 1g of sodium gluconate was added, and the reaction was pre-sodiumized at 35℃ for 7h. After the reaction was completed, the reaction solution was centrifuged at 6000r / min for 5min. The solid was taken out and washed three times with deionized water and ethanol respectively. After drying at 90℃ for 10h, it was pulverized to obtain the hard carbon precursor.
[0055] (3) The hard carbon precursor was placed in a plasma sintering furnace, and a voltage of 3.5V and a pressure of 24MPa were applied under an argon atmosphere. The temperature was increased to 1100℃ at a heating rate of 300℃ / min. After the carbonization reaction was carried out for 6 minutes, the material was naturally cooled to room temperature to obtain the pre-sodium hard carbon material.
[0056] Example 4
[0057] The method is the same as in Example 1, except that in step (1), the amount of aspartic acid used is 7g.
[0058] Example 5
[0059] The method of Example 1 differs in that, in step (1), the temperature of the pre-carbonization reaction is 800°C.
[0060] Example 6
[0061] The method is the same as in Example 1, except that in step (1), the amount of 45wt% phosphoric acid aqueous solution used is 3.3g.
[0062] Example 7
[0063] The method of Example 1 differs in that, in step (1), starch is replaced with an equal weight of phenolic resin.
[0064] Comparative Example 1
[0065] The method is the same as in Example 1, except that in step (1), the amount of aspartic acid used is 1g.
[0066] Comparative Example 2
[0067] The method is the same as in Example 1, except that in step (1), the amount of aspartic acid used is 9g.
[0068] Comparative Example 3
[0069] The method of Example 1 differs in that, in step (1), the temperature of the pre-carbonization reaction is 1000°C.
[0070] Comparative Example 4
[0071] The method is the same as in Example 1, except that in step (1), the amount of 45wt% phosphoric acid aqueous solution used is 5.6g.
[0072] Comparative Example 5
[0073] The method is the same as in Example 1, except that aspartic acid is not used in step (1).
[0074] Comparative Example 6
[0075] The method is the same as in Example 1, except that in step (1), an aqueous solution of phosphoric acid is not used.
[0076] Comparative Example 7
[0077] The method is the same as in Example 1, except that in step (2), sodium citrate is replaced with sodium carbonate.
[0078] Test case
[0079] The pre-sodium-modified hard carbon materials obtained in Examples 1-7 and Comparative Examples 1-7 were respectively made into negative electrode sheets and further assembled into sodium-ion half-cells. The specific steps are as follows: The obtained pre-sodium-modified hard carbon materials, carbon nanotubes and polyvinylidene fluoride were mixed with solvents N-methylpyrrolidone and anhydrous oxalic acid in a weight ratio of 95:1:4 to form a negative electrode slurry (solid content 90%), which was then coated on the surface of copper foil. After rolling (compact density of 2.5 g / cc), slitting and sheet forming processes, negative electrode sheets were formed. The negative electrode sheets were assembled into sodium-ion half-cells, wherein sodium metal sheet was used as counter electrode, ceramic separator was used as separator, and 1 mol / L NaPF6 / DME was used as electrolyte.
[0080] Electrochemical performance of the sodium-ion half-cell was tested on a SLAN-CT2001B battery testing system at a test temperature of 25℃ and an electrochemical window of 0-2.75V. The sodium-ion half-cell was subjected to rate charge-discharge tests at 0.2C (1C = 600mA / g) to obtain the total capacity (ramp capacity + plateau capacity), plateau capacity, initial coulombic efficiency (ICE), and cycle capacity. The results are shown in Table 1.
[0081] Table 1
[0082]
[0083]
[0084] As shown in Table 1, the pre-sodium-treated hard carbon materials prepared by the pre-sodium treatment method of the present invention in Examples 1-7 have excellent performance. Their Na content, total capacity, plateau capacity, initial coulombic efficiency and capacity after 300 cycles are all at a high level, effectively solving the problems of low energy density and poor cycle performance of sodium-ion batteries.
[0085] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.
Claims
1. A method for pre-sodiuming hard carbon materials, characterized in that, The method includes: (1) A carbon source, amino acids and phosphoric acid are mixed and pre-carbonized to obtain a doped carbon source; (2) Provide a dispersion containing the doped carbon source, surfactant and weak base, and introduce an organic sodium salt to carry out a pre-sodiumization reaction to obtain a hard carbon precursor; (3) The hard carbon precursor is subjected to a carbonization reaction to obtain a pre-sodiumized hard carbon material; The weight ratio of the carbon source to the amino acid is 1:0.4-1.4, and the temperature of the pre-carbonization reaction is 300-800℃.
2. The method according to claim 1, wherein, The weight ratio of the carbon source to the amino acid is 1:0.4-1; Preferably, the weight ratio of the carbon source to phosphoric acid is 1:0.1-0.3, more preferably 1:0.1-0.2; Preferably, the mixing time is 0.1-2 hours, more preferably 0.5-1 hour; Preferably, the temperature of the pre-carbonization reaction is 300-600℃; Preferably, the pre-carbonization reaction takes 2-8 hours, more preferably 2-5 hours; Preferably, the pre-carbonization reaction is carried out in an inert atmosphere, which is selected from one or more of nitrogen and argon.
3. The method according to claim 1 or 2, wherein, The weight ratio of the doped carbon source to the surfactant is 1: 0.05-0.25, preferably 1:0.05-0.15; Preferably, the weight ratio of the doped carbon source to the weak base is 1:0.5-2, more preferably 1:0.5-1; Preferably, the weight ratio of the doped carbon source to the organic sodium salt is 1:0.2-0.8, more preferably 1:0.2-0.6; Preferably, the temperature of the pre-sodiumization reaction is 15-60°C, more preferably 15-40°C; Preferably, the pre-sodiumization reaction takes 6-12 hours, more preferably 6-8 hours.
4. The method according to any one of claims 1-3, wherein, The voltage for the carbonization reaction is 3.2-4V, preferably 3.2-3.5V; Preferably, the pressure of the carbonization reaction is 20-30 MPa, more preferably 22-25 MPa; Preferably, the carbonization reaction temperature is 1100-1500℃, more preferably 1100-1300℃; Preferably, the carbonization reaction takes 5-12 minutes, more preferably 5-8 minutes; Preferably, the heating rate of the carbonization reaction is 200-500℃ / min, more preferably 300-400℃ / min; Preferably, the carbonization reaction is carried out in an inert atmosphere, which is selected from one or more of nitrogen and argon.
5. The method according to any one of claims 1-4, wherein, The solvent of the dispersion is selected from a mixture of organic solvent and water; Preferably, the volume ratio of the organic solvent to water is 1:2-6, more preferably 1:3-5; Preferably, the organic solvent is selected from one or more of methanol, ethanol, tetrahydrofuran, acetone and dioxane, and more preferably from one or more of methanol and ethanol; Preferably, the amount of solvent used is 10-50 mL, more preferably 15-30 mL, relative to 1 g of the doped carbon source.
6. The method according to any one of claims 1-5, wherein, The carbon source is selected from one or more of starch, maltodextrin, phenolic resin, epoxy resin, cellulose, glucose, sucrose, maltose, lactose and fructose, preferably one or more of starch, maltodextrin, phenolic resin and glucose; Preferably, the amino acid is selected from one or more of alanine, lysine, aspartic acid, glycine, serine, and tryptophan, and more preferably from one or more of alanine, lysine, and aspartic acid.
7. The method according to any one of claims 1-6, wherein, The surfactant is selected from one or more of hexadecyltrimethylammonium bromide, sodium fatty alcohol polyoxyethylene ether sulfate, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, polyoxyethylene fatty alcohol ether, and polysorbate, preferably one or more of hexadecyltrimethylammonium bromide, sodium dodecylbenzene sulfonate, and polysorbate; Preferably, the weak base is selected from one or more of potassium bicarbonate, sodium bicarbonate, ammonium bicarbonate, ammonia, and urea, and more preferably from one or more of ammonium bicarbonate and ammonia. Preferably, the organic sodium salt is selected from one or more of sodium carboxymethyl cellulose, sodium alginate, sodium gluconate, monosodium glutamate, sodium phytate, sodium citrate, and sodium lactate, and more preferably from one or more of sodium alginate, sodium gluconate, sodium phytate, and sodium citrate.
8. A pre-sodium-modified hard carbon material, characterized in that, The pre-sodium-modified hard carbon material is prepared by the pre-sodium-modification method of the hard carbon material according to any one of claims 1-7.
9. A negative electrode, characterized in that, The negative electrode comprises the pre-sodium hard carbon material as described in claim 8.
10. A sodium-ion battery, characterized in that, The sodium-ion battery includes the pre-sodium hard carbon material as described in claim 8 or the negative electrode as described in claim 9.