Asphalt-based soft and hard carbon porous composite nanosheet negative electrode material and preparation method and application thereof

Abstract

The invention discloses an asphalt-based soft and hard carbon porous composite nanosheet negative electrode material and a preparation method thereof, and belongs to the technical field of sodium ion battery negative electrode materials. Concentrated sulfuric acid treated coal liquefaction pitch is used as a hard carbon precursor, deoiled pitch is used as a soft carbon precursor, the concentrated sulfuric acid treated coal liquefaction pitch and the deoiled pitch are mixed with sodium chloride and zinc chloride in proportion, and the soft and hard carbon porous composite nanosheet is obtained after ball milling, pre-carbonization and high-temperature carbonization. Under the current density of 100mA. G <-1 >, the charging specific capacity reaches 269.6 mAh.g <-1 >, the first-circle coulombic efficiency reaches 60.36%, and the platform area capacity contribution is 54.41%. The asphalt-based soft and hard carbon porous composite nanosheet negative electrode material is prepared through a structure regulation and control strategy of preparing two-dimensional sheet-shaped hard carbon by a eutectic salt template method and a pre-carbonization regulation and control closed-pore structure, sufficient electrolyte wetting is realized, and through rapid conductivity of an electrode, a carrier transmission path is shortened, and structural stability is improved. And the salt template can be recycled to realize cyclic utilization.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium ion battery negative electrode materials, and specifically relates to a preparation method and application of an asphalt-based soft and hard carbon porous composite nanosheet negative electrode material. Background Art

[0002] The global demand for electrochemical energy storage technology is growing, which poses a challenge to advanced energy storage technologies such as ion batteries. Among them, lithium-ion batteries have the advantages of high energy density and long cycle life and occupy a dominant position among various types of ion batteries. However, the limited global reserves of lithium resources restrict their large-scale application. Compared with lithium-ion batteries, sodium-ion batteries have outstanding advantages in raw material costs, safety performance and other aspects, making them a candidate battery technology to replace lithium-ion battery technology. The commercial application of sodium-ion batteries mainly depends on the development of high-performance and low-cost battery negative electrodes. Among the many negative electrode materials in the sodium-ion battery system, asphalt-derived carbon negative electrode materials have become a research hotspot in recent years, especially hard carbon materials, because of their large d 002 Spacing, rich closed-pore structure, low price and high carbon yield make it an excellent carbon precursor for sodium ion battery negative electrode materials and can realize high value-added utilization of petroleum asphalt.

[0003] Due to their high degree of disorder, large interlayer distances, and abundant nanopores and defects, hard carbon materials can store more sodium ions, increasing battery capacity. However, their electrical conductivity is poor. Soft carbon materials typically have higher electrical conductivity and shorter interlayer spacing, which facilitates the rapid insertion and extraction of sodium ions, improving the battery's rate capability. Combining the high capacity of hard carbon with the good electrical conductivity of soft carbon may be a viable approach to obtaining soft and hard carbon composites with excellent sodium ion storage properties. Furthermore, to mitigate the volume expansion caused by sodium ion insertion and extraction, carbonaceous materials such as carbon nanospheres, carbon nanowires, carbon nanosheets, and their composites have attracted considerable attention in the structural design of sodium ion battery anode materials. Among them, two-dimensional carbon nanosheets have a large specific surface area, which enables sufficient electrolyte wetting, rapid electrical conductivity through the electrode, shortened carrier transport paths, and structural stability. The realization of soft and hard carbon composites and the regulation of their structure to prepare soft and hard carbon porous composite nanosheet anode materials have become a research focus. CN116454227A proposes a soft and hard carbon composite material made of biomass and soft carbon precursor in a mass ratio of 1: (1 to 1.5), prepared by pre-carbonization, ball milling, liquid phase coating and carbonization process, and having a structure of micropores and mesopores as well as hard carbon coated with soft carbon. CN114477130A discloses a method for preparing a hard carbon negative electrode material for sodium ion batteries using porous materials, wherein biomass material cork is made into a porous material, the pores are adjusted by using a method of pressing the porous material, and then the porous material is coated with asphalt to reduce the specific surface area and porosity of the prepared hard carbon negative electrode material. CN116199207B relates to a method for preparing coal tar pitch-based three-dimensional hierarchical porous carbon for lithium ion battery negative electrodes, wherein sodium carbonate and silicon dioxide are used as dual templates and coal tar pitch is used as a carbon source to prepare coal tar pitch-based three-dimensional hierarchical porous carbon. Summary of the Invention

[0004] The present invention aims to address the low electrical conductivity and the need to improve reversible capacity, cycle stability, and rate performance of existing carbon negative electrode materials. The present invention provides a pitch-based soft and hard carbon porous composite nanosheet negative electrode material, its preparation method, and application. By using coal liquefaction pitch as a hard carbon precursor and deoiled pitch as a soft carbon precursor through liquid-phase oxidation with oxygen-containing acid, and by using eutectic salt templates to assist planar morphology growth and pre-carbonization to control the closed-pore structure, a pitch-based soft and hard carbon porous composite nanosheet negative electrode material with high carbon yield and stable structure is prepared.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] The present invention provides a method for preparing a pitch-based soft and hard carbon porous composite nanosheet negative electrode material, comprising the following specific steps:

[0007] (1) Coal liquefaction pitch and concentrated sulfuric acid were mixed and stirred at 40° C. for 5 h, and then filtered, washed, and dried to obtain first particles;

[0008] (2) adding the first particles, deoiled asphalt, sodium chloride, and zinc chloride in a ball mill according to a certain proportion, and ball milling to obtain the second particles;

[0009] (3) placing the second particles into a hydrothermal kettle for low-temperature pre-carbonization to obtain third particles;

[0010] (4) The third particles are transferred to a tubular furnace for carbonization, washed with hydrochloric acid solution, washed with deionized water, filtered, and dried, and then carbonized for the second time to obtain the fourth particles, which are the asphalt-based soft and hard carbon porous composite nanosheet negative electrode materials.

[0011] In step (1) of the present invention, the coal liquefaction pitch has a softening point of 160-220°C. Before use, it is placed in a vacuum drying oven at 100°C and dried for 24 hours. Subsequently, the dried coal liquefaction pitch is mixed with concentrated sulfuric acid at a ratio of 2g:50mL, and the precipitate is filtered and washed with deionized water until the pH value of the filtrate is about 6, and then placed in a 100°C oven and dried for 12 hours.

[0012] In step (2) of the present invention, the softening point of the deoiled asphalt is 130-160°C, the mass ratio of the first particles, deoiled asphalt, sodium chloride and zinc chloride is 5-7:4:16:24, preferably 6:4:16:24, and the ball milling is carried out at a speed of 500-800 r / min for 4-8 hours.

[0013] In step (3) of the present invention, the low-temperature pre-carbonization condition is 160-200°C for 8h, preferably 180°C.

[0014] In step (4) of the present invention, the carbonization conditions are 700-900°C for 2h, preferably 900°C, a heating rate of 2-5°C / min, and a protective atmosphere of nitrogen or argon. The hydrochloric acid solution concentration is 2-4 mol / L, the washing time is 30 min, and then the filtrate is washed with deionized water until the pH value of the filtrate is about 6. The precipitate is filtered and placed in a 100°C oven to dry for 12h. The secondary carbonization conditions are 1100-1400°C for 2h, preferably 1300°C, a heating rate of 2-5°C / min, and a protective atmosphere of nitrogen or argon.

[0015] The present invention also provides a pitch-based soft and hard carbon porous composite nanosheet negative electrode material prepared by the above method, which exhibits an amorphous and two-dimensional structure.

[0016] The present invention provides the application of the above-mentioned asphalt-based soft and hard carbon porous composite nanosheet negative electrode material in sodium ion batteries. -1 At a current density of 1.5 GHz, the charge capacity reaches 269.6 mAh g -1 Its first-circle Coulomb efficiency reaches 60.36%, and the platform area capacity contribution is 54.41%.

[0017] The present invention uses coal liquefaction pitch as a hard carbon precursor and deoiled pitch as a soft carbon precursor, and cleverly combines a highly disordered hard carbon structure with a relatively ordered soft carbon structure to achieve a controllable soft and hard carbon composite structure. The hard carbon component can increase the sodium ion storage sites, while the soft carbon component can promote electronic conductivity and improve structural stability. The synergistic effect between the hard carbon and soft carbon components can restructure the microcrystalline structure and improve the reversible capacity, cycle stability and rate performance of the carbon negative electrode material. The asphalt-based soft and hard carbon porous composite nanosheet negative electrode material presents an amorphous and two-dimensional structure. The two-dimensional carbon nanosheet has a large specific surface area, which can achieve sufficient electrolyte wetting, rapid conductivity through the electrode, shortened carrier transmission path and structural stability.

[0018] Compared with the prior art, the technical effects achieved by the present invention are:

[0019] 1. The method of preparing soft and hard carbon using coal liquefaction pitch and deoiled pitch as precursors is simple and feasible, with low raw material cost, and can be used for large-scale preparation of asphalt-based soft and hard carbon porous composite nanosheet negative electrode materials.

[0020] 2. The asphalt-based soft and hard carbon porous composite nanosheet negative electrode material prepared by the present invention is first pre-oxidized by coal liquefaction asphalt, and then mixed with deoiled asphalt and salt template by ball milling, and a lamellar porous structure is obtained by pre-carbonization and high-temperature carbonization.

[0021] 3. The asphalt-based soft and hard carbon porous composite nanosheet negative electrode material prepared by the present invention has the following advantages: Improved electrical conductivity: The hard carbon negative electrode material prepared by pre-oxidation of conventional asphalt-based materials has three-dimensional layered graphite-like microcrystals, which are beneficial for sodium ion storage, but excessive oxygen content reduces the electrical conductivity of the material. The soft carbon component can promote electronic conductivity and improve structural stability. The synergistic effect between the hard carbon and soft carbon components can restructure the microcrystalline structure and improve the reversible capacity, cycle stability and rate performance of the carbon negative electrode material. The structural control strategy of preparing two-dimensional sheet-like hard carbon by the eutectic salt template method can achieve sufficient electrolyte wetting, rapid conductivity through the electrode, shortened carrier transmission path and structural stability, and the salt template can be recycled for recycling. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a flow chart for preparing the pitch-based soft and hard carbon porous composite nanosheet negative electrode material of the present invention;

[0023] Figure 2 This is an SEM image of the pitch-based soft and hard carbon porous composite nanosheet negative electrode material prepared in Example 1 of the present invention;

[0024] Figure 3 The asphalt-based soft and hard carbon porous composite nanosheet negative electrode material prepared in Example 1 of the present invention is subjected to a 100 mA·g -1Constant current charge and discharge curve at current density. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below with reference to the examples, but the embodiments of the present invention are not limited thereto. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in the field or in the product instructions were used. Raw materials used, where the manufacturer is not specified, are all conventional products that can be purchased commercially.

[0026] Example 1:

[0027] (1) Coal liquefaction pitch with a softening point of 160°C was placed in a vacuum drying oven at 100°C for 24 h. 2 g of the dried coal liquefaction pitch was added to a beaker containing 50 mL of concentrated sulfuric acid. The mixture was then stirred at 40°C for 5 h. The precipitate was filtered and washed with deionized water until the pH value of the filtrate was approximately 6. The first particles were obtained after drying in a 100°C oven for 12 h.

[0028] (2) 6 g of the first particles, 4 g of deoiled asphalt with a softening point of 160°C, 16 g of sodium chloride, and 24 g of zinc chloride were added to a ball mill and ball milled at a speed of 500 r / min for 8 h to obtain the second particles;

[0029] (3) The second particles were placed in a hydrothermal reactor and carbonized at 180°C for 8 h to obtain the third particles;

[0030] (4) The third particle was transferred to a tubular furnace and carbonized at 900°C for 2 h (heating rate 5°C / min, protective atmosphere is nitrogen). After natural cooling, it was washed with 4 mol / L hydrochloric acid solution for 30 min, washed with deionized water until the pH of the filtrate was about 6, filtered and precipitated, and dried in a 100°C oven for 12 h. After carbonization at 1400°C for 2 h (heating rate 5°C / min, protective atmosphere is nitrogen), the fourth particle was obtained, which is the asphalt-based soft and hard carbon porous composite nanosheet negative electrode material.

[0031] Example 2:

[0032] (1) Coal liquefaction pitch with a softening point of 180°C was placed in a vacuum drying oven at 100°C for 24 h. 2 g of the dried coal liquefaction pitch was added to a beaker containing 50 mL of concentrated sulfuric acid. The mixture was then stirred at 40°C for 5 h. The precipitate was filtered and washed with deionized water until the pH value of the filtrate was approximately 6. The first particles were obtained after drying in a 100°C oven for 12 h.

[0033] (2) 5 g of the first particles, 4 g of deoiled asphalt with a softening point of 130°C, 16 g of sodium chloride, and 24 g of zinc chloride were added to a ball mill and ball milled at 800 r / min for 4 h to obtain the second particles;

[0034] (3) placing the second particles in a hydrothermal autoclave and carbonizing them at 200 °C for 8 h to obtain the third particles;

[0035] (4) The third particle was transferred to a tubular furnace and carbonized at 700°C for 2 h (heating rate 2°C / min, protective atmosphere is argon). After natural cooling, it was washed with 2 mol / L hydrochloric acid solution for 30 min, washed with deionized water until the pH of the filtrate was about 6, filtered, and dried in a 100°C oven for 12 h. After carbonization at 1300°C for 2 h (heating rate 2°C / min, protective atmosphere is argon), the fourth particle was obtained, which is the asphalt-based soft and hard carbon porous composite nanosheet negative electrode material.

[0036] Example 3:

[0037] (1) Coal liquefaction pitch with a softening point of 160°C was placed in a vacuum drying oven at 100°C for 24 h. 2 g of the dried coal liquefaction pitch was added to a beaker containing 50 mL of concentrated sulfuric acid. The mixture was then stirred at 40°C for 5 h. The precipitate was filtered and washed with deionized water until the pH value of the filtrate was approximately 6. The first particles were obtained after drying in a 100°C oven for 12 h.

[0038] (2) 7 g of the first particles, 4 g of deoiled asphalt with a softening point of 160°C, 16 g of sodium chloride, and 24 g of zinc chloride were added to a ball mill and ball milled at 700 r / min for 4.5 h to obtain the second particles;

[0039] (3) placing the second particles in a hydrothermal autoclave and carbonizing them at 160°C for 8 h to obtain the third particles;

[0040] (4) The third particle was transferred to a tubular furnace and carbonized at 800°C for 2 h (heating rate 3°C / min, protective atmosphere is argon). After natural cooling, it was washed with 3 mol / L hydrochloric acid solution for 30 min, washed with deionized water until the pH of the filtrate was about 6, filtered and precipitated, and dried in a 100°C oven for 12 h. After carbonization at 1100°C for 2 h (heating rate 3°C / min, protective atmosphere is argon), the fourth particle was obtained, which is the asphalt-based soft and hard carbon porous composite nanosheet negative electrode material.

[0041] Example 4:

[0042] (1) Coal liquefaction pitch with a softening point of 220°C was placed in a vacuum drying oven at 100°C for 24 h. 2 g of the dried coal liquefaction pitch was added to a beaker containing 50 mL of concentrated sulfuric acid. The mixture was then stirred at 40°C for 5 h. The precipitate was filtered and washed with deionized water until the pH value of the filtrate was approximately 6. The first particles were obtained after drying in a 100°C oven for 12 h.

[0043] (2) 6.5 g of the first particles, 4 g of deoiled asphalt with a softening point of 140°C, 16 g of sodium chloride, and 24 g of zinc chloride were added to a ball mill and ball milled at a speed of 600 r / min for 5.5 h to obtain the second particles;

[0044] (3) placing the second particles in a hydrothermal autoclave and carbonizing them at 200 °C for 8 h to obtain the third particles;

[0045] (4) The third particle was transferred to a tubular furnace and carbonized at 850°C for 2 h (heating rate 5°C / min, protective atmosphere is nitrogen). After natural cooling, it was washed with 2 mol / L hydrochloric acid solution for 30 min, washed with deionized water until the pH of the filtrate was about 6, filtered, and dried in a 100°C oven for 12 h. After carbonization at 1300°C for 2 h (heating rate 5°C / min, protective atmosphere is nitrogen), the fourth particle was obtained, which is the asphalt-based soft and hard carbon porous composite nanosheet negative electrode material.

[0046] Example 5:

[0047] (1) Coal liquefaction pitch with a softening point of 210°C was placed in a vacuum drying oven at 100°C for 24 h. 2 g of the dried coal liquefaction pitch was added to a beaker containing 50 mL of concentrated sulfuric acid. The mixture was then stirred at 40°C for 5 h. The precipitate was filtered and washed with deionized water until the pH value of the filtrate was approximately 6. The first particles were then dried in a 100°C oven for 12 h.

[0048] (2) 5.5 g of the first particles, 4 g of deoiled asphalt with a softening point of 150°C, 16 g of sodium chloride, and 24 g of zinc chloride were added to a ball mill and ball milled at 500 r / min for 7 h to obtain the second particles;

[0049] (3) placing the second particles in a hydrothermal autoclave and carbonizing them at 190°C for 8 h to obtain the third particles;

[0050] (4) The third particle was transferred to a tubular furnace and carbonized at 900°C for 2 h (heating rate 2°C / min, protective atmosphere is argon). After natural cooling, it was washed with 2 mol / L hydrochloric acid solution for 30 min, washed with deionized water until the pH of the filtrate was about 6, filtered, and dried in a 100°C oven for 12 h. After carbonization at 1400°C for 2 h (heating rate 2°C / min, protective atmosphere is argon), the fourth particle was obtained, which is the asphalt-based soft and hard carbon porous composite nanosheet negative electrode material.

[0051] Test example:

[0052] Preparation of electrode plates. The fourth particles prepared in Example 1, conductive carbon black, and binder polyvinylidene fluoride were weighed in a mass ratio of 80:10:10 and mixed evenly in a mortar. An appropriate amount of N-methylpyrrolidone solvent was added and stirred to prepare a slurry. The slurry was evenly coated on aluminum foil and dried in a vacuum drying oven at 120°C for 12 hours. The slurry was then cut into 12 mm round negative electrode plates for later use.

[0053] The button cell assembly was carried out in a double-station glove box filled with argon atmosphere (H2O, O2 < 0.01 ppm). The prepared hard carbon material electrode was used as the negative electrode, 1M NaClO4 (volume ratio of EC / DEC = 1:1) was used as the electrolyte, and the metal sodium (Na) sheet was used as the counter electrode to assemble the button cell.

[0054] The assembled 2032 button cells were charged and discharged on a constant current test system with a voltage range of 0.005-3.0V.

[0055] In the same manner, the pitch-based soft and hard carbon porous composite nanosheet negative electrode materials prepared in Examples 2-4 were made into sodium ion button batteries and subjected to charge and discharge tests.

[0056] Figure 1 This is a flow chart for preparing the asphalt-based soft and hard carbon porous composite nanosheet negative electrode material described in the present invention. Figure 2 This is an SEM image of the pitch-based soft and hard carbon porous composite nanosheet negative electrode material prepared in Example 1 of the present invention. It can be seen from the figure that the prepared pitch-based soft and hard carbon porous composite nanosheet negative electrode material presents an amorphous and two-dimensional structure. Figure 3 The asphalt-based soft and hard carbon porous composite nanosheet negative electrode material prepared in Example 1 of the present invention is subjected to a 100 mA·g -1 Constant current charge and discharge curves at a current density of 100mA·g -1 At a current density of 1.5 GHz, the charge capacity can reach 269.6 mAh g -1 , its first-circle Coulomb efficiency can reach 60.36%, and the platform area capacity contribution is 54.41%.

Claims

1. A method for preparing a pitch-based soft and hard carbon porous composite nanosheet negative electrode material, characterized in that: The following steps are involved: (1) Coal liquefaction pitch and concentrated sulfuric acid were mixed and stirred at 40° C. for 5 h, and then filtered, washed, and dried to obtain first particles; (2) adding the first particles, deoiled asphalt, sodium chloride, and zinc chloride in a ball mill according to a certain proportion, and ball milling to obtain the second particles; (3) placing the second particles into a hydrothermal kettle for low-temperature pre-carbonization to obtain third particles; (4) The third particles are transferred to a tubular furnace for carbonization, washed with hydrochloric acid solution, washed with deionized water, filtered, and dried, and then carbonized for the second time to obtain the fourth particles, which are the asphalt-based soft and hard carbon porous composite nanosheet negative electrode materials.

2. The method for preparing a pitch-based soft and hard carbon porous composite nanosheet negative electrode material according to claim 1, characterized in that: The softening point of the coal liquefaction pitch described in step (1) is 160-220°C. Before use, it is placed in a vacuum drying oven at 100°C and dried for 24 hours. The ratio of the dried coal liquefaction pitch to concentrated sulfuric acid is 2g:50mL.

3. The method for preparing a pitch-based soft and hard carbon porous composite nanosheet negative electrode material according to claim 1, characterized in that: The softening point of the deoiled asphalt in step (2) is 130-160°C.

4. The method for preparing a pitch-based soft and hard carbon porous composite nanosheet negative electrode material according to claim 1, characterized in that: In step (2), the mass ratio of the first particles, deoiled asphalt, sodium chloride and zinc chloride is 5-7:4:16:

24.

5. The method for preparing a pitch-based soft and hard carbon porous composite nanosheet negative electrode material according to claim 1, characterized in that: The low-temperature pre-carbonization condition in step (3) is carbonization at 160-200° C. for 8 hours.

6. The method for preparing a pitch-based soft and hard carbon porous composite nanosheet negative electrode material according to claim 1, characterized in that: The carbonization conditions in step (4) are as follows: first, carbonize at 700-900°C for 2h, with a heating rate of 2-5°C / min, and a protective atmosphere of nitrogen or argon; after natural cooling, wash with 2-4mol / L hydrochloric acid solution for 30min, wash with deionized water until the filtrate pH is about 6, filter the precipitate and dry it in a 100°C oven for 12h, and the secondary carbonization conditions are carbonization at 1100-1400°C for 2h, with a heating rate of 2-5°C / min, and a protective atmosphere of nitrogen or argon.

7. A pitch-based soft and hard carbon porous composite nanosheet negative electrode material prepared by the preparation method according to any one of claims 1 to 6.

8. The pitch-based soft and hard carbon porous composite nanosheet negative electrode material according to claim 7, characterized in that: Pitch-based soft and hard carbon porous composite nanosheet negative electrode materials exhibit amorphous and two-dimensional structures.

9. Use of the pitch-based soft and hard carbon porous composite nanosheet negative electrode material according to any one of claims 7 to 8 in the preparation of sodium ion batteries.

10. The use according to claim 9, characterized in that Pitch-based soft and hard carbon porous composite nanosheet anode materials at 100 mA·g -1 At a current density of 1.5 GHz, the charge capacity reaches 269.6 mAh g -1 Its first-circle Coulomb efficiency reaches 60.36%, and the platform area capacity contribution is 54.41%.

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