Method for preparing carbon anode material for sodium ion battery by one-step phosphoric acid activation method

Abstract

The application discloses a method for preparing a carbon negative electrode material of a sodium ion battery by one-step phosphoric acid activation, and specifically comprises the following steps: step 1, a certain amount of high coalification degree semi-coke blocks are crushed into powder; step 2, the product of step 1 is subjected to acid washing or alkali washing to remove ash in the powder; step 3, the product of step 2 is mixed with concentrated phosphoric acid according to a certain mass ratio and then placed in an oven for drying; step 4, the product of step 3 is subjected to high-temperature carbonization; and step 5, the product of step 4 is subjected to screening treatment to obtain the carbon negative electrode material. The application solves the problem that the interlayer spacing of high coalification degree semi-coke after one-step carbonization is too low and does not meet the requirement of the interlayer spacing of a sodium ion negative electrode material.

Description

Technical Field

[0001] This invention belongs to the technical field of battery anode material preparation methods, and relates to a one-step phosphoric acid activation method for preparing sodium-ion battery carbon anode materials. Background Technology

[0002] Lithium-ion batteries are green, pollution-free, and have high specific energy, making them the preferred material for next-generation green batteries. However, due to limited lithium resources, 75% of China's lithium resources are concentrated in salt lakes, which have a high magnesium-to-lithium ratio and are difficult to extract, so most lithium resources currently need to be imported. Sodium-ion batteries, on the other hand, are widely available, inexpensive, have long cycle life, and good safety, and are expected to replace lithium-ion batteries in low-speed electric vehicles and energy storage. However, due to the decline in lithium carbonate prices, the cost advantage of sodium-ion batteries over lithium-ion batteries is no longer significant. To maintain its position in the fierce competition, sodium-ion batteries urgently need to improve their cost-effectiveness, that is, to enhance their performance while maintaining their cost advantage.

[0003] Among sodium-ion battery anode materials, soft / hard carbon materials have the greatest industrialization advantage, with biomass hard carbon materials being the most widely used. Coal-based carbon anode materials, prepared using coal as a precursor, are soft carbon anode materials, offering advantages such as a low voltage plateau, high sodium storage capacity, simple production, low cost, and ease of industrialization. Unlike the lithium storage mechanism of graphite, the sodium storage mechanism of soft / hard carbon anodes is more complex, involving both slope adsorption and plateau intercalation, requiring specific interlayer spacing D in the carbon anode material. 002 ≥0.37nm is more conducive to the shuttle of sodium ions in the carbon layer.

[0004] Semi-coke, as a pre-processing product of coal chemical industry, is currently often used to replace raw coal for power generation, with advantages including being environmentally friendly, having low volatile matter content, and being inexpensive. When lump coal is used to prepare soft carbon for sodium-ion batteries, pre-processing requires steps such as pre-carbonization and acid washing. Comparing the production process of semi-coke, it was found that semi-coke can be used as a precursor for soft carbon in sodium-ion batteries, not only being inexpensive but also environmentally friendly, thus broadening the applications of semi-coke. Semi-coke sold on the market is divided into two types: low-coalification semi-coke and high-coalification semi-coke. Low-coalification semi-coke is a lump carbon material obtained by treating bituminous coal at 600–650℃, while high-coalification semi-coke is obtained by treating bituminous coal at 800–950℃. Statistics show that most semi-coke sold on the market is high-coalification semi-coke. However, the sodium storage capacity of the carbon anode material obtained after one-step carbonization of high-coalification semi-coke at 900–1150℃ is limited—approximately 220 mAh / g. This is because the high temperature results in excessively low interlayer spacing (D0). 002 <0.37nm), which does not conform to the interlayer spacing D of sodium ion anode materials. 002 The requirement of ≥0.37nm is not conducive to sodium ion shuttle movement. Therefore, how to introduce most commercially available high-coalification semi-coke into the sodium-ion battery anode material system at low cost is an urgent challenge to be solved. Summary of the Invention

[0005] The purpose of this invention is to provide a one-step phosphoric acid activation method for preparing carbon anode materials for sodium-ion batteries, which solves the problem in the prior art where the interlayer spacing of high-coalification-degree charcoal is too low after one-step carbonization, failing to meet the interlayer spacing requirements of sodium-ion anode materials.

[0006] The technical solution adopted in this invention is a one-step phosphoric acid activation method for preparing carbon anode materials for sodium-ion batteries, which is implemented according to the following steps:

[0007] Step 1: Weigh a certain amount of high coalification degree semi-coke blocks and crush them into powder;

[0008] Step 2: Acid washing or alkali washing is performed on the product from Step 1 to remove ash from the powder;

[0009] Step 3: Mix the product from Step 2 with concentrated phosphoric acid at a certain mass ratio and then dry it in an oven.

[0010] Step 4: Carbonize the product from Step 3 at high temperature;

[0011] Step 5: The product from step 4 is sieved to obtain carbon anode material.

[0012] The invention is further characterized in that:

[0013] Step 1 specifically involves: weighing a certain amount of high-coalification-degree semi-coke blocks and crushing them to obtain high-coalification-degree semi-coke powder, wherein the particle size D in the powder is... 50 It is 5-7 μm.

[0014] In step 2, the acid washing uses one or more of dilute hydrochloric acid, sulfuric acid, nitric acid, oxalic acid, or hydrofluoric acid; the alkaline washing uses one of potassium hydroxide solution, sodium hydroxide solution, or calcium hydroxide solution.

[0015] In step 3, the product of step 2 is mixed with concentrated phosphoric acid at a mass ratio of 10:(1-20).

[0016] In step 3, drying involves drying the moisture in an oven at 80°C.

[0017] Step 4 is as follows:

[0018] The product from step 3 is placed in a high-temperature tubular furnace. Inert gas is introduced into the furnace until the pressure inside the furnace is greater than the standard atmospheric pressure and the purity of the inert gas is greater than or equal to 98%. The gas outlet of the furnace is opened, and the inert gas is kept flowing. The temperature is increased from room temperature to 250-400°C at a rate of 0.5°C / min to 5°C / min, and held for 1-3 hours. Then, the furnace is heated to 800-1200°C at a rate of 1-20°C / min and held for 2-10 hours. After the holding period, the temperature is reduced to room temperature at a rate of 1-10°C / min.

[0019] The inert gas is at least one of nitrogen, argon, and helium.

[0020] Step 5 specifically involves sieving the product from step 4 to control the particle size to be no larger than 10 μm, thereby obtaining the final carbon anode material.

[0021] The beneficial effects of this invention are:

[0022] (1) The present invention uses concentrated phosphoric acid as an activator to attach P element to the surface of high coalification degree semi-coke, which solves the problem in the prior art that the interlayer spacing of high coalification degree semi-coke after one-step carbonization is too low and does not meet the requirement that the interlayer spacing of sodium ion anode material is greater than or equal to 0.37nm.

[0023] (2) The present invention further carbonizes commercially available high-coalification semi-coke on the basis of activation with concentrated phosphoric acid, so that the carbon atoms of the semi-coke are rearranged to generate semi-coke-based carbon materials, which greatly improves the first efficiency and capacity of semi-coke-based carbon materials as anode materials for sodium-ion batteries. The reversible charging specific capacity of the semi-coke-based carbon materials applied to sodium-ion batteries can reach 270mAh / g.

[0024] (3) The preparation method of the present invention is simple and easy to implement. Attached Figure Description

[0025] Figure 1 This is a comparison chart of the sodium storage charge-discharge curves of the carbon anode material prepared in Example 2 of the present invention and the carbon anode material prepared by the one-step carbonization method in Comparative Example 1.

[0026] Figure 2 This is a comparison chart of sodium storage charge-discharge curves of high-coalification-degree semi-coke and low-coalification-degree semi-coke sold on the market after undergoing a one-step carbonization process.

[0027] Figure 3 These are the XRD diffraction patterns of commercially available high-coalification-degree and low-coalification-degree semi-coke after a one-step carbonization process.

[0028] Figure 4 These are XRD diffraction patterns of the sodium-ion battery carbon anode materials prepared in Embodiments 1-3 and Comparative Example 1 of this invention. Detailed Implementation

[0029] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0030] The present invention discloses a one-step phosphoric acid activation method for preparing carbon anode materials for sodium-ion batteries, which is implemented according to the following steps:

[0031] Step 1: Weigh a certain amount of high-coalification semi-coke blocks and pulverize them using air jet milling. The resulting high-coalification semi-coke powder is the first matrix. The particle size D in the powder is... 50 It is 5-7 μm;

[0032] Step 2: The first matrix is ​​acid-washed or alkali-washed to remove ash from the powder to obtain the second matrix. The acid washing uses one or more of dilute hydrochloric acid, sulfuric acid, nitric acid, oxalic acid, and hydrofluoric acid; the alkali washing uses one of potassium hydroxide solution, sodium hydroxide solution, or calcium hydroxide solution.

[0033] Step 3: After mixing the second matrix with concentrated phosphoric acid at a certain mass ratio, place it in an 80℃ oven to dry the moisture to obtain the third matrix. The second matrix and concentrated phosphoric acid are mixed at a mass ratio of 10:(1-20).

[0034] Step 4: Place the third matrix into a high-temperature tubular furnace, and introduce inert gas into the furnace until the pressure inside the furnace is greater than the standard atmospheric pressure and the purity of the inert gas is greater than or equal to 98%. Open the gas outlet of the high-temperature furnace and keep the inert gas flowing. Increase the temperature from room temperature to 250-400℃ at a heating rate of 0.5℃ / min to 5℃ / min, and hold for 1-3 hours. Then, increase the temperature of the furnace to 800-1200℃ at a heating rate of 1-20℃ / min and hold for 2-10 hours. After holding, cool down to room temperature at a rate of 1-10℃ / min to obtain the fourth matrix. The inert gas is at least one of nitrogen, argon, and helium.

[0035] Step 5: The fourth matrix is ​​sieved to control the particle size to no more than 10 μm, thus obtaining the final carbon anode material.

[0036] The commercially available high-coalification semi-coke used in Examples 1-7 and Comparative Examples 1-2 of this invention was Wuzhou semi-coke purchased from northern Shaanxi.

[0037] Example 1

[0038] A one-step phosphoric acid activation method for preparing carbon anode materials for sodium-ion batteries is as follows:

[0039] Step 1: Weigh a certain amount of commercially available high-coalification semi-coke, and perform preliminary refining by air jet milling to obtain the first matrix, controlling the particle size D in the coal-based powder. 50 The size is 5μm to 7μm;

[0040] Step 2: The first matrix obtained in Step 1 is acid-washed with dilute hydrochloric acid and hydrofluoric acid to remove some of the ash in the powder and obtain the second matrix.

[0041] Step 3: Mix the second matrix obtained in Step 2 with concentrated phosphoric acid at a ratio of 10:20 (i.e., a mass ratio of 1 / 2), and then dry the moisture in an 80°C oven to obtain the third matrix.

[0042] Step 4: Calcine the third matrix obtained in step 3 under an inert atmosphere to obtain the fourth matrix. The temperature is increased from room temperature to 300℃ at a rate of 3℃ / min and held for 3 hours. Then the temperature is increased to 1200℃ and held for 3 hours. During this period, gas circulation is maintained. After calcination, the temperature is reduced to room temperature at a rate of 5℃ / min. The material obtained is the fourth matrix.

[0043] Step 5: The fourth matrix obtained in Step 4 is subjected to sieving to control the particle size to no more than 10 μm, and finally sodium-carbon anode material based on high coalification degree styrene activated by phosphoric acid is obtained.

[0044] Example 2

[0045] A one-step phosphoric acid activation method for preparing carbon anode materials for sodium-ion batteries is as follows:

[0046] Step 1: Weigh a certain amount of commercially available high-coalification semi-coke, and perform preliminary refining by air jet milling to obtain the first matrix, controlling the particle size D in the coal-based powder. 50 The size is 5μm to 7μm;

[0047] Step 2: The first matrix obtained in Step 1 is acid-washed with dilute hydrochloric acid and hydrofluoric acid to remove some of the ash in the powder and obtain the second matrix.

[0048] Step 3: Mix the second matrix obtained in Step 2 with concentrated phosphoric acid at a mass ratio of 10 / 10, and then dry the mixture in an 80°C oven to obtain the third matrix.

[0049] Step 4: Calcine the third matrix obtained in step 3 under an inert atmosphere to obtain the fourth matrix. The temperature is increased from room temperature to 350℃ at a rate of 2℃ / min and held for 2 hours. Then the temperature is increased to 1150℃ and held for 2 hours. During this period, gas circulation is maintained. After calcination, the temperature is reduced to room temperature at a rate of 5℃ / min. The material obtained is the fourth matrix.

[0050] Step 5: The fourth matrix obtained in Step 4 is subjected to sieving to control the particle size to no more than 10 μm, and finally sodium-carbon anode material based on high coalification degree styrene activated by phosphoric acid is obtained.

[0051] Example 3

[0052] A one-step phosphoric acid activation method for preparing carbon anode materials for sodium-ion batteries is as follows:

[0053] Step 1: Weigh a certain amount of commercially available high-coalification semi-coke, and perform preliminary refining by air jet milling to obtain the first matrix, controlling the particle size D in the coal-based powder. 50 The size is 5μm to 7μm;

[0054] Step 2: The first matrix obtained in Step 1 is acid-washed with dilute hydrochloric acid and hydrofluoric acid to remove some of the ash in the powder and obtain the second matrix.

[0055] Step 3: Mix the second matrix obtained in Step 2 with concentrated phosphoric acid at a ratio of 10:5 (mass ratio 2 / 1) until homogeneous, and then dry the moisture in an 80°C oven to obtain the third matrix.

[0056] Step 4: The third matrix obtained in Step 3 is calcined in an inert atmosphere to obtain the fourth matrix. The temperature is increased from room temperature to 300℃ at a heating rate of 1℃ / min and held for 1.5h. Then the temperature is increased to 1150℃ at a heating rate of 3℃ / min and held for 3h. During the process, gas is kept circulating. After calcination, the temperature is reduced to room temperature at a rate of 5℃ / min. The material obtained is the fourth matrix.

[0057] Step 5: The fourth matrix obtained in Step 4 is subjected to sieving to control the particle size to no more than 10 μm, and finally sodium-carbon anode material based on high coalification degree styrene activated by phosphoric acid is obtained.

[0058] Example 4

[0059] A one-step phosphoric acid activation method for preparing carbon anode materials for sodium-ion batteries is as follows:

[0060] Step 1: Weigh a certain amount of commercially available high-coalification semi-coke, and perform preliminary refining by air jet milling to obtain the first matrix, controlling the particle size D in the coal-based powder. 50 The size is 5μm to 7μm;

[0061] Step 2: The first matrix obtained in Step 1 is acid-washed with dilute hydrochloric acid and hydrofluoric acid to remove some of the ash in the powder and obtain the second matrix.

[0062] Step 3: Mix the second matrix obtained in Step 2 with concentrated phosphoric acid at a ratio of 10:10 (mass ratio 1 / 1) until homogeneous, and then dry the moisture in an oven at 80°C to obtain the third matrix.

[0063] Step 4: The third matrix obtained in Step 3 is calcined in an inert atmosphere to obtain the fourth matrix. The temperature is increased from room temperature to 350°C at a heating rate of 1.5°C / min and held for 1 hour. Then the temperature is increased to 1100°C at a heating rate of 5°C / min and held for 2 hours. During the process, gas is kept circulating. After calcination, the temperature is reduced to room temperature at a rate of 5°C / min. The material obtained is the fourth matrix.

[0064] Step 5: The fourth matrix obtained in Step 4 is subjected to sieving to control the particle size to no more than 10 μm, and finally sodium-carbon anode material based on high coalification degree styrene activated by phosphoric acid is obtained.

[0065] Example 5

[0066] A one-step phosphoric acid activation method for preparing carbon anode materials for sodium-ion batteries is as follows:

[0067] Step 1: Weigh a certain amount of commercially available high-coalification semi-coke, and perform preliminary refining by air jet milling to obtain the first matrix, controlling the particle size D in the coal-based powder. 50 The size is 5μm to 7μm;

[0068] Step 2: The first matrix obtained in Step 1 is acid-washed with dilute hydrochloric acid and hydrofluoric acid to remove some of the ash in the powder and obtain the second matrix.

[0069] Step 3: After mixing the second matrix obtained in step 2 with concentrated phosphoric acid at a mass ratio of 10:6, place the mixture in an 80°C oven to dry the moisture and obtain the third matrix.

[0070] Step 4: The third matrix obtained in Step 3 is calcined in an inert atmosphere to obtain the fourth matrix. The temperature is increased from room temperature to 320°C at a heating rate of 2°C / min and held for 2 hours. Then the temperature is increased to 1200°C at a heating rate of 2°C / min and held for 2 hours. During the process, gas is kept circulating. After calcination, the temperature is reduced to room temperature at a rate of 5°C / min. The material obtained is the fourth matrix.

[0071] Step 5: The fourth matrix obtained in Step 4 is subjected to sieving to control the particle size to no more than 10 μm, and finally sodium-carbon anode material based on high coalification degree styrene activated by phosphoric acid is obtained.

[0072] Example 6

[0073] A one-step phosphoric acid activation method for preparing carbon anode materials for sodium-ion batteries is as follows:

[0074] Step 1: Weigh a certain amount of commercially available high-coalification semi-coke, and perform preliminary refining by air jet milling to obtain the first matrix, controlling the particle size D in the coal-based powder. 50 The size is 5μm to 7μm;

[0075] Step 2: The first matrix obtained in Step 1 is acid-washed with dilute hydrochloric acid and hydrofluoric acid to remove some of the ash in the powder and obtain the second matrix.

[0076] Step 3: After mixing the second matrix obtained in Step 2 with concentrated phosphoric acid at a mass ratio of 10:4, place the mixture in an 80°C oven to dry the moisture and obtain the third matrix.

[0077] Step 4: The third matrix obtained in Step 3 is calcined in an inert atmosphere to obtain the fourth matrix. The temperature is increased from room temperature to 350°C at a heating rate of 1°C / min and held for 2 hours. Then the temperature is increased to 1100°C at a heating rate of 5°C / min and held for 3 hours. During the process, gas is kept circulating. After calcination, the temperature is reduced to room temperature at a rate of 5°C / min. The material obtained is the fourth matrix.

[0078] Step 5: The fourth matrix obtained in Step 4 is subjected to sieving to control the particle size to no more than 10 μm, and finally sodium-carbon anode material based on high coalification degree styrene activated by phosphoric acid is obtained.

[0079] Example 7

[0080] A one-step phosphoric acid activation method for preparing carbon anode materials for sodium-ion batteries is as follows:

[0081] Step 1: Weigh a certain amount of commercially available high-coalification semi-coke, and perform preliminary refining by air jet milling to obtain the first matrix, controlling the particle size D in the coal-based powder. 50 The size is 5μm to 7μm;

[0082] Step 2: The first matrix obtained in Step 1 is acid-washed with dilute hydrochloric acid and hydrofluoric acid to remove some of the ash in the powder and obtain the second matrix.

[0083] Step 3: After mixing the second matrix obtained in Step 2 with concentrated phosphoric acid at a mass ratio of 10:3, place the mixture in an 80°C oven to dry the moisture and obtain the third matrix.

[0084] Step 4: The third matrix obtained in Step 3 is calcined in an inert atmosphere to obtain the fourth matrix. The temperature is increased from room temperature to 400℃ at a heating rate of 1℃ / min and held for 1 hour. Then the temperature is increased to 1200℃ at a heating rate of 3℃ / min and held for 2 hours. During the process, gas is kept circulating. After calcination, the temperature is reduced to room temperature at a rate of 5℃ / min. The material obtained is the fourth matrix.

[0085] Step 5: The fourth matrix obtained in Step 4 is subjected to sieving to control the particle size to no more than 10 μm, and finally sodium-carbon anode material based on high coalification degree styrene activated by phosphoric acid is obtained.

[0086] Comparative Example 1

[0087] A one-step carbonization method is used to process high-coal-degree semi-coke to prepare semi-coke-based sodium anode materials, specifically as follows:

[0088] Step 1: Weigh a certain amount of commercially available high-coalification semi-coke, and perform preliminary refining by air jet milling to obtain the first matrix, controlling the particle size D in the coal-based powder. 50 Less than 8μm;

[0089] Step 2: Acid washing is performed on the first matrix obtained in Step 1 to remove ash, resulting in the second matrix;

[0090] Step 3: Calcine the second substrate obtained in Step 2 at 1150℃ to finally obtain a semi-coke-based sodium electrode anode material based on a one-step carbonization method.

[0091] Comparative Example 2

[0092] The preparation of semi-coke-based sodium anode materials using an alkaline activation method for treating high-coal-grade semi-coke is as follows:

[0093] Step 1: Weigh a certain amount of commercially available high-coalification semi-coke, and perform preliminary refining by air jet milling to obtain the first matrix, controlling the particle size D in the coal-based powder. 50 Less than 8μm;

[0094] Step 2: Mix the first matrix obtained in Step 1 with 15% by mass of potassium hydroxide until homogeneous to obtain the second matrix;

[0095] Step 3: Calcine the second matrix obtained in Step 2 at 800℃ to obtain the third matrix;

[0096] Step 4: After acid washing with dilute hydrochloric acid and hydrofluoric acid, the third matrix obtained in step 3 is dried to obtain the fourth matrix;

[0097] Step 5: Calcine the fourth substrate obtained in Step 4 at 1150℃ to finally obtain the semi-coke-based sodium electrode anode material prepared by the alkali activation method.

[0098] The carbon materials prepared in Examples 1-7 and Comparative Examples 1-2 were used as anode materials for sodium-ion batteries.

[0099] The prepared carbon material powder was mixed with acetylene black and sodium alginate binder at a mass ratio of 90:5:5. A suitable amount of water was added and the mixture was ground to form a slurry. The uniformly ground slurry was then evenly coated onto the current collector aluminum foil. After drying, it was punched into an electrode sheet with a diameter of 12 mm. Under vacuum conditions, the electrode sheet was dried at 120°C for 10 hours and then transferred to a glove box for later use.

[0100] The simulated battery assembly was performed in an Ar atmosphere glove box, using metallic sodium as the counter electrode and 1 mole of NaPF6 dissolved in 1 L of a 1:1 volume ratio solution of ethylene carbonate and diethyl carbonate as the electrolyte, to assemble a CR2032 coin cell. Constant current charge-discharge mode was used, and charge-discharge tests were conducted at a current density of C / 10. The test results are shown in Table 1 below, with a discharge cutoff voltage of 0V and a charge cutoff voltage of 2V.

[0101] Table 1 Comparison of Test Results

[0102] 2.0V discharge (mAh / g) 2.0V charge (mAh / g) 2.0V initial efficiency (%) Example 1 of the present application 315 270 85.7 Example 2 of the present application 326.55 279.16 85.5 Example 3 of the present application 316.2 274.18 86.7 Example 4 of the present application 308.2 272.8 88.5 Example 5 of the present application 312.6 277.7 88.8 Example 6 of the present application 292.27 270.77 92.6 Example 7 of the present application 295 271.3 92.0 Comparative Example 1 283.09 243.8 86.12 Comparative Example 2 296.4 246.8 83.27

[0103] As shown in Table 1, compared with the one-step carbonization method (Comparative Example 1) and the alkali activation method (Comparative Example 2), the sodium storage capacity of the soft carbon material obtained by the one-step phosphoric acid activation method of the present invention is significantly improved.

[0104] This invention achieves low-cost development of commercially available high-coalification semi-coke through a one-step phosphoric acid activation method. Currently, over 80% of commercially available semi-coke is high-coalification, with only a small portion being low-coalification. Therefore, the supply of high-coalification semi-coke exceeds demand. Figure 2 The figure shows the sodium storage electrochemical properties of carbon materials obtained after high-temperature carbonization of low-coalification-degree semi-coke (LLT) and high-coalification-degree semi-coke (GLT) raw materials. Figure 2 It can be seen that, under the same voltage, the sodium storage capacity of high coalification degree semi-coke (GLT) is significantly lower than that of low coalification degree semi-coke. High coalification degree semi-coke (GLT) that is directly carbonized in one step cannot meet the conditions for application in sodium ion anode materials. Figure 3 The images show the XRD diffraction patterns of low-coalification and high-coalification semi-coke raw materials after high-temperature calcination (1150℃). Figure 3 It can be seen that the interlayer spacing of raw materials with different degrees of coalification varies. The high-coalification semi-coke in Comparative Example 1, after high-temperature calcination, shows D... 002 The nanometer diameter (D) of low-coalification semi-coke is 0.36 nm after calcination at 1150 °C. 002 The interlayer spacing of high-coalification semi-coke is approximately 0.378 nm, which is lower than that of low-coalification semi-coke and clearly does not meet the requirement of ≥0.37 nm for sodium ion anode materials. However, this invention uses a one-step phosphoric acid activation method to treat high-coalification semi-coke, enabling it to meet the requirements of sodium ion anode materials. The treatment method is green and simple, using concentrated phosphoric acid as the treatment solution, which is low-cost and enables the low-cost application of commercially available high-coalification semi-coke in the preparation of sodium ion anode materials.

[0105] This invention employs a one-step phosphoric acid activation method. Phosphoric acid is an effective activator for improving the performance of carbon-based materials, causing phosphorus to adhere to the surface of semi-coke, forming functional groups such as P=O, POP, and POC. Phosphorus is one of the anode materials with the highest capacity, which is beneficial for maximizing sodium storage capacity. H3PO4 has low corrosivity, resulting in fewer harmful residues in the product and making it environmentally friendly. The semi-coke-based carbon anode produced by the one-step carbonization method of high-coalification semi-coke has a low interlayer spacing, resulting in a reversible charging specific capacity of only 220 mAh / g. After carbonization with a certain amount of concentrated phosphoric acid according to this invention, the reversible charging specific capacity can reach 270 mAh / g, with a maximum of 279.16 mAh / g (Example 2).

[0106] Figure 1 The figures show the sodium storage electrochemical performance curves of the carbon anode materials obtained in Example 2 (one-step phosphoric acid activation method) and Comparative Example 1 (one-step carbonization). By comparison, under the same voltage, the sodium storage electrochemical performance of the carbon material obtained by treating high-coalification-degree blue char with the one-step phosphoric acid activation method of the present invention is significantly higher than that of the carbon material obtained by one-step carbonization of high-coalification-degree blue char. This indicates that the sodium storage capacity of high-coalification-degree blue char treated by the method of the present invention as a sodium ion anode material is significantly improved.

[0107] like Figure 4 As shown, compared with the high coalification degree semi-coke that has not been activated by concentrated phosphoric acid, the peak angle of the material treated by the one-step phosphoric acid activation method of the present invention is significantly shifted to the left. The interlayer spacing of the carbon anode materials prepared in Examples 1, 2, 3 and Comparative Example 1 was calculated using Bragg's formula. The interlayer spacing of Examples 1, 2, 3 and Comparative Example 1 is 0.371 nm, 0.373 nm, 0.372 nm and 0.366 nm, respectively. This indicates that the interlayer spacing of the high coalification degree semi-coke treated by the one-step phosphoric acid activation method of the present invention significantly meets the interlayer spacing requirements of carbon anode materials, which is more conducive to sodium ion transport.

Claims

1. A method for preparing carbon anode materials for sodium-ion batteries via a one-step phosphoric acid activation method, characterized in that, The specific steps are as follows: Step 1: Weigh a certain amount of high-coalification-degree semi-coke blocks and crush them to obtain high-coalification-degree semi-coke powder. The particle size D of the powder is... 50 It is 5-7 μm; Step 2: The product from Step 1 is subjected to acid washing or alkaline washing to remove ash from the powder; wherein, acid washing uses one or more of dilute hydrochloric acid, sulfuric acid, nitric acid or oxalic acid, hydrofluoric acid; the alkaline solution used for alkaline washing is one of potassium hydroxide solution, sodium hydroxide solution or calcium hydroxide solution. Step 3: Mix the product from Step 2 with concentrated phosphoric acid at a mass ratio of 10:(1-20) and place it in an 80℃ oven to dry the moisture. Step 4: The product from Step 3 is subjected to high-temperature carbonization, specifically as follows: The product from step 3 is placed in a high-temperature tube furnace. Inert gas is introduced into the high-temperature tube furnace until the pressure inside the furnace is greater than the standard atmospheric pressure and the purity of the inert gas inside the furnace is greater than or equal to 98%. The gas outlet of the high-temperature tube furnace is opened, and the inert gas is kept flowing. The temperature is increased from room temperature to 250-400℃ at a heating rate of 0.5℃ / min to 5℃ / min, and held for 1-3 hours. Then, the high-temperature tube furnace is heated to 800-1200℃ at a heating rate of 1-20℃ / min and held for 2-10 hours. After the holding is completed, the temperature is reduced to room temperature at a rate of 1-10℃ / min. Step 5: The product from step 4 is sieved to obtain carbon anode material.

2. The method for preparing sodium-ion battery carbon anode material by one-step phosphoric acid activation according to claim 1, characterized in that, The inert gas is at least one of nitrogen, argon, and helium.

3. The method for preparing sodium-ion battery carbon anode material by one-step phosphoric acid activation according to claim 1, characterized in that, Step 5 specifically involves sieving the product from step 4 to control the particle size to be no greater than 10 μm, thereby obtaining the final carbon anode material.

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