Preparation method of low-polarized sodium ion battery lignite-based hard carbon negative electrode material

Abstract

The application discloses a preparation method of a low-polarization lignite-based hard carbon negative electrode material for a sodium ion battery, and the method comprises the following steps: step (1), performing acid washing treatment and washing and drying on a crushed lignite precursor to obtain a hard carbon precursor; and step (2), performing pre-carbonization and high-temperature carbonization treatment on the hard carbon precursor after the acid treatment in a protective atmosphere to obtain the lignite-based hard carbon negative electrode material. The method takes lignite as a precursor of the hard carbon negative electrode material, adjusts the pore structure and graphitization degree of the lignite by adding simple acid washing, and obtains the lignite-based hard carbon negative electrode material with excellent electrochemical performance. The preparation process is simple, the efficiency is high, and the cost is low. When the lignite-derived hard carbon negative electrode material is applied to the sodium ion battery, not only can high capacity and high initial coulombic efficiency be realized, but also the electrode polarization can be effectively reduced, excellent rate performance is exhibited, and the problem that the rate performance of the hard carbon negative electrode material for the sodium ion battery is not ideal is solved.

Description

Technical Field

[0001] This invention relates to a method for preparing sodium-ion anode materials, specifically a method for preparing lignite-based hard carbon anode materials for low-polarity sodium-ion batteries. Background Technology

[0002] Due to its economic advantages and excellent electrochemical performance, sodium-ion batteries are considered one of the most competitive candidates for grid-scale energy storage devices. However, the development of anode materials severely restricts their commercial application. As the most successful commercial anode material for lithium-ion batteries, graphite's relatively narrow interlayer spacing (<0.37 nm) and the larger radius of sodium ions compared to lithium ions result in a mismatch, leading to poor sodium storage performance. In contrast, hard carbon has a unique microstructure composed of pores, defects, and graphite microcrystals. It is abundant, inexpensive, and can achieve capacities exceeding 300 mAh / g even at lower discharge voltages, demonstrating significant commercial potential. Nevertheless, in practical applications, electrode polarization results in unsatisfactory rate performance. This can lead to sodium deposition in full-cell devices, severely impacting battery performance and even posing safety hazards. Therefore, reducing electrochemical polarization and improving rate performance have become crucial aspects of current hard carbon anode material development.

[0003] Lignite, a low-rank coal, is abundant and extremely inexpensive (approximately 100-300 RMB / ton). However, its direct carbonization easily produces a partially graphitized structure and has a high ash content. Therefore, finding a simple preparation process to achieve the industrial production of lignite-based hard carbon anode materials with excellent rate performance is of great significance for the development of sodium-ion batteries. Summary of the Invention

[0004] This invention provides a method for preparing a lignite-based hard carbon anode material for low-polarity sodium-ion batteries. The method uses lignite as a precursor for the hard carbon anode material, and adjusts its pore structure and graphitization degree through simple acid washing to obtain a lignite-based hard carbon anode material with excellent electrochemical performance. The preparation process is simple, efficient, and low-cost. When the obtained lignite-derived hard carbon anode material is applied to sodium-ion batteries, it not only achieves both high capacity and high initial coulombic efficiency, but also effectively reduces electrode polarization, exhibiting excellent rate performance. This solves the problem of unsatisfactory rate performance of hard carbon anode materials in sodium-ion batteries.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A method for preparing a lignite-based hard carbon anode material for low-polarity sodium-ion batteries includes the following steps:

[0007] Step (1) The pulverized lignite precursor is acid-washed and dried to obtain a hard carbon precursor, wherein: the lignite raw material is low-rank lignite with a carbon content of 55~75 wt% and an ash content of 5~25 wt%; the acid solution for acid washing is one or more of nitric acid, sulfuric acid, hydrochloric acid, hydrofluoric acid, and phosphoric acid, with pH=1~5 and a concentration of 0.1~1.0 M, preferably 0.2~0.6 M; the mass percentage of lignite raw material in the acid solution is 10~40%; and the acid washing time is 2~24 h, preferably 4~12 h.

[0008] Step (2) The acid-treated hard carbon precursor is pre-carbonized and high-temperature carbonized in a protective atmosphere to obtain lignite-based hard carbon anode material. The protective atmosphere is one or more of nitrogen, helium, neon, and argon, preferably nitrogen and / or argon. The high-temperature calcination apparatus used for pre-carbonization and high-temperature carbonization includes, but is not limited to, tubular furnaces, Joule furnaces, graphite furnaces, etc. The pre-carbonization heating rate is 2~10 ℃ / s, the carbonization temperature is 350~550 ℃, preferably 400~500 ℃, and the holding time is 60~240 min. The high-temperature carbonization heating rate is 2~10 ℃ / s, the carbonization temperature is 1100~1600 ℃, preferably 1300~1500 ℃, and the holding time is 60~240 min. The particle size D50 of the lignite-based hard carbon anode material is 3~20 μm, and the specific surface area is ≤25 m². 2 / g, tap density is 0.5~1.1 g / cm³ 3 The first coulombic efficiency is ≥85%, and the first-cycle reversible specific capacity is ≥300 mAh / g.

[0009] Application of a lignite-based hard carbon anode material for sodium-ion batteries prepared by the above method in the field of energy storage sodium-ion batteries.

[0010] Compared with the prior art, the present invention has the following advantages:

[0011] The lignite-based hard carbon anode material for sodium-ion batteries prepared by this invention has extremely low cost (lignite raw material costs about 100-300 yuan / ton, far lower than biomass). At the same time, it can effectively adjust the structure of the hard carbon material. Using this hard carbon material as the anode material for sodium-ion batteries can achieve both high capacity and high initial coulombic efficiency, and effectively reduce electrochemical polarization and improve the rate performance of the electrode. Attached Figure Description

[0012] Figure 1 This is a transmission electron microscope (TEM) image of the lignite-based hard carbon anode material for sodium-ion batteries prepared in Example 1.

[0013] Figure 2 The graph shows the rate performance of the lignite-based hard carbon anode material for sodium-ion batteries in Example 1, obtained by testing at different current densities.

[0014] Figure 3 This is a comparison of the first charge-discharge curves of the lignite-based hard carbon anode material for sodium-ion batteries in Example 1 at a current density of 50 mA / g. Detailed Implementation

[0015] The technical solution of the present invention will be further described below with reference to the accompanying drawings, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0016] Example 1

[0017] This embodiment provides a method for preparing a lignite-based hard carbon anode material for low-polarity sodium-ion batteries, the method comprising the following steps:

[0018] (1) Cut the selected lignite raw material (carbon content of about 65% and ash content of about 15%) and put it into a crusher to crush it. After sieving, lignite material powder (30~50 mesh) is obtained and stored.

[0019] (2) The material prepared in step (1) is treated with sulfuric acid solution with a sulfuric acid concentration of 0.5 M, the mass ratio of lignite powder to sulfuric acid solution is 15%, and the stirring time is 8 h;

[0020] (3) After filtering, washing and drying the material obtained in step (2), put it into a tube furnace, introduce nitrogen gas, heat up at a rate of 5 ℃ / s, carbonize at a temperature of 450 ℃, and hold for 60 min to obtain pre-carbonized material.

[0021] (4) Nitrogen gas is introduced into the material obtained in step (3) at a heating rate of 5 ℃ / s, a carbonization temperature of 1400 ℃, and a holding time of 180 min to obtain a lignite-based hard carbon anode material for sodium-ion batteries, labeled as RHC-1.

[0022] In this embodiment, acid washing effectively removes minerals and unstable oxygen-containing functional groups from lignite, thereby inducing the formation of ideal nanoscale closed pores during carbonization (providing "pore-filling" sodium storage sites) and regulating a short-range ordered, long-range disordered turbine-like layered structure (expanding the carbon interlayer spacing to over 0.37 nm, providing a low-barrier, rapid diffusion channel for sodium ions and reducing polarization). Furthermore, the removal of functional groups inhibits the formation of active defect sites, reducing irreversible consumption of the SEI film. Ultimately, the treated lignite forms a three-dimensional porous, interconnected amorphous carbon framework, whose well-developed ion migration network promotes electrolyte wetting and alleviates concentration polarization at high rates.

[0023] Figure 1This is a transmission electron microscope (TEM) image of the lignite-based hard carbon anode material for sodium-ion batteries prepared in this embodiment. Figure 1 The presence of clearly ordered short-range graphite microcrystals and abundant closed-pore structures indicates that the interlayer spacing and disorder of the hard carbon prepared by this method are significantly altered. This provides more kinetically reversible sodium storage active sites, which is beneficial for improving the rate performance of the material.

[0024] Figure 2 This image shows the rate performance of the lignite-based hard carbon anode material for sodium-ion batteries prepared in this embodiment, tested at different current densities. Figure 2 It can be seen that when the current density is 5000 mA / g, the capacity is 75 mAh / g.

[0025] Figure 3 This is a comparison of the first-cycle charge-discharge curves of the lignite-based hard carbon anode material for sodium-ion batteries prepared in this embodiment at a current density of 50 mA / g. Figure 3 As can be seen, the initial coulombic efficiency of the coal-based hard carbon material is ≥86%, and the initial reversible specific capacity is ≥330 mAh / g.

[0026] Example 2

[0027] This embodiment provides a method for preparing a lignite-based hard carbon anode material for low-polarity sodium-ion batteries, the method comprising the following steps:

[0028] (1) Cut the selected lignite raw material into a crusher and crush it. After screening, obtain lignite material powder and store it.

[0029] (2) The material obtained in step (1) is treated with sulfuric acid solution with a sulfuric acid concentration of 0.3 M, the mass ratio of lignite powder to sulfuric acid solution is 15%, and the stirring time is 8 h;

[0030] (3) After filtering, washing and drying the material obtained in step (2), put it into a tube furnace, introduce nitrogen gas, heat up at a rate of 5 ℃ / s, carbonize at a temperature of 450 ℃, and hold for 60 min to obtain pre-carbonized material.

[0031] (4) Nitrogen gas is introduced into the material obtained in step (3) at a heating rate of 5 ℃ / s, a carbonization temperature of 1400 ℃, and a holding time of 180 min to obtain a lignite-based hard carbon anode material for sodium-ion batteries, labeled as RHC-2.

[0032] Example 3

[0033] This embodiment provides a method for preparing a lignite-based hard carbon anode material for low-polarity sodium-ion batteries, the method comprising the following steps:

[0034] (1) Cut the selected lignite raw material into a crusher and crush it. After screening, obtain lignite material powder and store it.

[0035] (2) The material prepared in step (1) was treated with hydrochloric acid solution with a concentration of 0.6 M, the mass ratio of lignite powder to hydrochloric acid solution was 15%, and the stirring time was 8 h.

[0036] (3) After filtering, washing and drying the material obtained in step (2), put it into a tube furnace, introduce nitrogen gas, heat up at a rate of 5 ℃ / s, carbonize at a temperature of 450 ℃, and hold for 60 min to obtain pre-carbonized material.

[0037] (4) Nitrogen gas is introduced into the material obtained in step (3) at a heating rate of 5 ℃ / s, a carbonization temperature of 1400 ℃, and a holding time of 180 min to obtain a lignite-based hard carbon anode material for sodium-ion batteries, labeled as RHC-3.

[0038] Example 4

[0039] This embodiment provides a method for preparing a lignite-based hard carbon anode material for low-polarity sodium-ion batteries, the method comprising the following steps:

[0040] (1) Cut the selected lignite raw material into a crusher and crush it. After screening, obtain lignite material powder and store it.

[0041] (2) The material prepared in step (1) is treated with sulfuric acid solution with a sulfuric acid concentration of 0.5 M, the mass ratio of lignite powder to sulfuric acid solution is 25%, and the stirring time is 8 h;

[0042] (3) After filtering, washing and drying the material obtained in step (2), put it into a tube furnace, introduce nitrogen gas, heat up at a rate of 5 ℃ / s, carbonize at a temperature of 450 ℃, and hold for 60 min to obtain pre-carbonized material.

[0043] (4) Nitrogen gas is introduced into the material obtained in step (3) at a heating rate of 5 ℃ / s, a carbonization temperature of 1400 ℃, and a holding time of 180 min to obtain a lignite-based hard carbon anode material for sodium-ion batteries, labeled as RHC-4.

[0044] Example 5

[0045] This embodiment provides a method for preparing a lignite-based hard carbon anode material for low-polarity sodium-ion batteries, the method comprising the following steps:

[0046] (1) Cut the selected lignite raw material into a crusher and crush it. After screening, obtain lignite material powder and store it.

[0047] (2) The material prepared in step (1) is treated with sulfuric acid solution with a sulfuric acid concentration of 0.5 M, the mass ratio of lignite powder to sulfuric acid solution is 15%, and the stirring time is 12 h;

[0048] (3) After filtering, washing and drying the material obtained in step (2), put it into a tube furnace, introduce nitrogen gas, heat up at a rate of 5 ℃ / s, carbonize at a temperature of 450 ℃, and hold for 60 min to obtain pre-carbonized material.

[0049] (4) Nitrogen gas is introduced into the material obtained in step (3) at a heating rate of 5 ℃ / s, a carbonization temperature of 1400 ℃, and a holding time of 180 min to obtain a lignite-based hard carbon anode material for sodium-ion batteries, labeled as RHC-5.

[0050] Application Example 1

[0051] (1) The prepared hard carbon sample RHC-1 was ground into fine particles using a mortar and pestle in a drying room and sieved through a 300-mesh sieve. Electrode slurry was prepared according to a mass ratio of active material to binder (2% sodium alginate solution) of 95:5. It was uniformly coated on aluminum foil, dried overnight at 90°C in an oven, cut into 10 mm circular electrode sheets, and assembled into sodium-ion half-cells in a glove box under argon protection.

[0052] (2) Sodium-ion half-cell assembly and testing: Sodium metal was used as the counter electrode and 1M NaPF6+DEGDME (1:1) was used as the electrolyte. Sodium-ion half-cells were assembled in a glove box under argon protection. The assembled cells were sealed using a button cell sealing machine. After being taken out of the glove box, the cells were left to stand at room temperature for 12 hours.

[0053] The electrochemical performance of the prepared sodium-ion half-cell was tested using a LAND CT2001A meter. Specifically, the charge specific capacity (mAh / g) was measured within a voltage range of 0-2 V at current densities of 20, 50, 100, 200, 500, 1000, 2000, 3000, 4000, and 5000 mA / g, demonstrating good rate performance. At a current density of 5000 mA / g, the capacity was 75 mAh / g.

Claims

1. A method for preparing a lignite-based hard carbon anode material for low-polarity sodium-ion batteries, characterized in that... The method includes the following steps: Step (1) The pulverized lignite precursor is acid-washed, washed and dried to obtain hard carbon precursor; Step (2) The acid-treated hard carbon precursor is pre-carbonized and high-temperature carbonized in a protective atmosphere to obtain lignite-based hard carbon anode material.

2. The preparation method of the low-polarization sodium-ion battery lignite-based hard carbon anode material according to claim 1, characterized in that... In step (1), the lignite raw material is low-rank lignite with a carbon content of 55-75 wt% and an ash content of 5-25 wt%.

3. The preparation method of the low-polarization sodium-ion battery lignite-based hard carbon anode material according to claim 1, characterized in that... In step (1), the acid solution for pickling is one or more of nitric acid, sulfuric acid, hydrochloric acid, hydrofluoric acid, and phosphoric acid, with pH=1~5 and concentration of 0.1~1.0 M. The mass percentage of lignite raw material in the acid solution is 10~40%, and the pickling time is 2~24 h.

4. The preparation method of the low-polarization sodium-ion battery lignite-based hard carbon anode material according to claim 3, characterized in that... The concentration of the acid solution is 0.2~0.6 M, and the pickling time is 4~12 h.

5. The method for preparing the low-polarization sodium-ion battery lignite-based hard carbon anode material according to claim 1, characterized in that... In step (2), the protective atmosphere is one or more of nitrogen, helium, neon, and argon.

6. The method for preparing the low-polarization sodium-ion battery lignite-based hard carbon anode material according to claim 5, characterized in that... The protective atmosphere is nitrogen and / or argon.

7. The method for preparing the low-polarization sodium-ion battery lignite-based hard carbon anode material according to claim 1, characterized in that... In step (2), the high-temperature calcination device used for pre-carbonization and high-temperature carbonization is a tubular furnace, a Joule furnace or a graphite furnace; the heating rate of pre-carbonization is 2~10 ℃ / s, the carbonization temperature is 350~550 ℃, and the holding time is 60~240 min; the heating rate of high-temperature carbonization is 2~10 ℃ / s, the carbonization temperature is 1100~1600℃, and the holding time is 60~240 min.

8. The method for preparing the low-polarization sodium-ion battery lignite-based hard carbon anode material according to claim 7, characterized in that... The carbonization temperature for pre-carbonization is 400~500℃; the carbonization temperature for high-temperature carbonization is 1300~1500℃.

9. A low-polarization sodium-ion battery lignite-based hard carbon anode material prepared by the method according to any one of claims 1-8.

10. The application of a low-polarization sodium-ion battery lignite-based hard carbon anode material prepared by the method according to any one of claims 1-8 in the field of energy storage sodium-ion batteries.

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